Ultrasound and Thermography As Psychophysiological

ULTRASOUND AND THERMOGRAPHY AS PSYCHOPHYSIOLOGICAL

MEASURES OF SEXUAL AROUSAL IN MEN AND WOMEN

Tuuli M. Kukkonen

Department of Psychology

McGill University

Montreal, Canada

May 2010

A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Doctor of Philosophy

TABLE OF CONTENTS

Abstract…………………………………………………………………………………i

Résumé………………………………………………………………………………...iii

Contribution of Authors………………………………………………………………..v

Statement of Original Contributions………………………………………………....vi

Acknowledgements……………………………………………………………………ix

Introduction……………………………………………………………………………...1

References……………………………………………………………………...4

Literature Review………………………………………………………………… ……6

References…………………………………………………………………….14

Convergent and Discriminant Validity of Clitoral Color Doppler Ultrasonography as a Measure of Sexual Arousal

Abstract………………………………………………………………………...24

Introduction…………………………………………………………………….25

Materials and Methods……………………………………………………….26

Results………………………………………………………………………....29

Discussion……………………………………………………………………..30

References…………………………………………………………………….34

Table 1………………………………………………………………………….37

Transitional Text 1…………………………………………………………………...... 38

Thermography as a Physiological Measure of Sexual Arousal in Both Men and Women

Abstract……………………………………………………………………...…41

Introduction………………………………………………………………….....43

Materials and Methods…………………………………………………….....49

Results………………………………………………………………………….58

Discussion…………………………………………………………………...... 65

Conclusions…………………………………………………………………....71

References………………………………………………………………….....73

Table 1………………………………………………………………………….81

Table 2………………………………………………………………………….82

Figure 1……………………………………………………………………...…83

Figure 2…………………………………………………………………...……84

Figure 3………………………………………………………………...………85

Transitional Text 2……………………………………………………………………..86

An Evaluation of the Validity of Thermography as a Physiological Measure of Sexual Arousal in a Non-University Adult Sample

Abstract……………………………………………………………………...…88

Introduction…………………………………………………………...………..89

Method………………………………………………………………………….92

Results…………………………………………………………………...…...102

Discussion………………………………………………………………...….112

References…………………………………………………………………...123

Appendix……………………………………………………………………...131

Table 1……………………………………………………………………...... 133

Table 2……………………………………………………………………...... 134

Figure 1…………………………………………………………………….....135

Figure 2…………………………………………………………………….....136

Figure 3…………………………………………………………………….....137

Update on Literature Review………………………………………………………..138

References…………………………………………………………………...141

General Conclusions and Future Directions………………………………………143

References…………………………………………………………………...149

Appendix………………………………………………………………………………152

ABSTRACT

Current physiological measures of sexual arousal are intrusive, hard to compare between genders, quantitatively problematic and not clinically useful. The goal of this thesis was to examine alternative methods of measuring sexual arousal through the use of ultrasonography and thermography. In the first empirical study, the validity of clitoral ultrasound as a measure of female sexual arousal was examined. Results indicated that standard ultrasound measures (peak systolic velocity, end diastolic velocity and resistance index) did not differentiate participants in the sexual arousal condition from those in a pleasant arousal control condition. Furthermore, none of the ultrasound measures were correlated with self-reported sexual arousal. In the second empirical investigation, thermography was evaluated as a measure of sexual arousal in both men and women. Results from this study demonstrated that genital temperature as measured by thermography could detect and differentiate sexual arousal from neutral and pleasant arousal control conditions. In addition, genital temperature was significantly correlated with self-reported sexual arousal for both men and women. In the third empirical investigation, the use of thermography as a measure of sexual arousal was examined in a sample of 30-45 year old men and women. Results were similar to the second study in that genital temperature was significantly greater for participants in the sexual arousal condition as compared to neutral, pleasant arousal and anxiety control conditions. i

Additionally, continuous measurement of self-reported sexual arousal was significantly correlated with genital temperature change for both men and women. Together, this body of work demonstrates the potential utility of thermography as a measurement tool to study sexual arousal.

RESUMÉ

Les mesures courantes étudiants l'excitation sexuelle posent des difficultés en ce qui concerne la comparaison des sexes, et sont indiscrètes, quantitativement problématiques et cliniquement inutiles.

L'objectif de cette thèse était d'examiner des méthodes alternatives qui mesurent l'excitation sexuelle, à travers l'utilisation de l'ultrasonographie et de la thermographie. Dans la première étude empirique, la validité des ultrasons clitoridiens comme mesure d'excitation sexuelle féminine à été examiné. Les résultats ont indiqué que les mesures standards d'ultrasons

(vélocité systolique maximale, vélocité diastolique terminale et l'index de résistance) n'ont pas différencié les participants de la condition d'excitation sexuelle avec ceux du groupe témoin d'excitation plaisante. En outre, aucune des mesures d'ultrasons était en corrélation avec les degrés d'excitation sexuelle perçus. Lors de la seconde investigation empirique, la thermographie comme mesure d'excitation sexuelle chez les hommes et les femmes a été évalué. Les résultats de cette étude ont démontré que la température génitale mesuré par la thermographie pouvait détecter et différencier l'excitation sexuelle des autres formes d'excitations. De plus, la température génitale a corrélé significativement avec les degrés d'excitation sexuelle perçus chez les hommes et les femmes. Durant la troisième expérience, l'usage de la thermographie comme mesure d'excitation sexuel a été examiné avec un échantillon d'hommes et de femmes âgé(e)s entre 30-45 ans. Les résultats étaient similaires à ceux iii

de la seconde expérience, où la température génitale étaient significativement plus élevée chez le groupe soumis aux conditions d'excitation sexuelle que chez le groupe témoin soumis à des conditions neutres, d'excitation plaisante ou d'anxiété. En outre, la mesure continue d'excitation sexuelle perçue était en corrélation significative avec le changement dans la température génitale chez les hommes et les femmes. L'ensemble du travail démontre l'utilité potentielle de la thermographie comme outil de mesure pour étudier l'excitation sexuelle.

CONTRIBUTION OF AUTHORS

This thesis consists of three papers. The first paper is co-authored by myself, Laurel Paterson, Francine Bouvier, Rhonda Amsel, and Drs.

Yitzchak Binik and Samir Khalifé. The second and third papers are co- authored by myself, Rhonda Amsel, and Drs. Yitzchak Binik and Serge

Carrier. The following is a statement regarding the contributions of the various authors to the three papers.

The ultrasound paper resulted from a research study, which was elaborated, conducted, analyzed and written by myself. Drs. Binik and

Khalifé served in an advisory capacity during the formulation of research questions and the development of the protocol, and in an editorial capacity during the writing of the final manuscript. Dr. Khalifé and Francine Bouvier conducted the ultrasound assessments for the participants. Rhonda

Amsel served as a statistical consultant and Laurel Paterson served in an editorial capacity.

The second and third papers resulted from two research studies, which were elaborated, conducted, analyzed and written by myself. Drs.

Binik and Carrier served in an advisory capacity during the formulation of the research questions and the development of the protocol, and in an editorial capacity during the writing of the final manuscript. Rhonda Amsel served as a statistical consultant.

STATEMENT OF ORIGINAL CONTRIBUTIONS v

This dissertation is a manuscript-based thesis comprised of three peer-reviewed publications that provide original contributions to the field of sexual psychophysiology. The first paper entitled “Clitoral color Doppler ultrasonography as a measure of female sexual arousal” was published in

2006 in the Journal of Sex and Marital Therapy, volume 32, pp. 281-287.

This manuscript was the first publication to examine the ability of clitoral ultrasound to discriminate between sexual arousal from a non-sexual pleasant arousal state, humor. It is also one of the first published papers

(see Redouté et al., 2000 for exception) to use humor as a control condition in sexual psychophysiology, and the first to examine the relationship between ultrasound measures and subjective reports of sexual arousal. The results from this paper indicate that clitoral Doppler ultrasonography does not differentiate between sexual arousal and a pleasant arousal state. Furthermore, none of the ultrasound measures were correlated with subjective sexual arousal. These results and the limitations of the ultrasound procedure suggest that this technology requires further examination before being adopted as a widely used method for the study of sexual arousal.

The second manuscript entitled “Thermography as a physiological measure of sexual arousal in men and women” was published in 2007 in the Journal of Sexual Medicine, volume 4, pp. 93-105. This publication was the first to examine a modern thermographic camera as an instrument to measure sexual response in men and women. Additionally, this is the vi

first publication to report on a technology that can provide a continuous recording of sexual arousal without requiring any physical contact with participants. Results from this study demonstrated that thermography can be used to detect and differentiate sexual arousal from control conditions in both men and women and that genital temperature is significantly correlated with subjective sexual arousal. Additionally, these results demonstrate similarities between men and women in the time to peak sexual response. These positive results provide initial support for a new method of measuring sexual arousal that is less intrusive than previous instruments and can be used to directly compare sexes.

The third manuscript entitled “An evaluation of the validity of thermography as a physiological measure of sexual arousal in a non- university adult sample” will be published in the August 2010 issue of the

Archives of Sexual Behavior, volume 39 (DOI 10.1007/s 10508-009-9496-

4). This publication provides the first replication of modern thermography as a measure of sexual arousal. In addition, it is the first publication to examine the ability of thermography to differentiate between sexual arousal and an anxiety provoking stimulus, and the first to examine the within-subject correlation between thermographic measures and a continuous measure of subjective sexual arousal. The results from this publication provide evidence that thermography can detect and differentiate sexual arousal from control conditions in a 30-45 year old sample of healthy men and women. In addition, the results demonstrate a vii

significant relationship between subjective sexual arousal and physiological measures, indicating that thermography has much potential as a methodology to assess sexual responding in men and women.

Reference

Redouté, J., Stoleru, S., Gregoire, M. C., Costes, N., Cinotti, L., Lavenne,

F., et al. (2000). Brain processing of visual sexual stimuli in human

males. Human Brain Mapping,11, 162-77.

viii

ACKNOWLEDGEMENTS

This dissertation and my journey through graduate school would not have been possible without the incredible support that I have received from numerous individuals over the years. First and foremost I would like to thank my supervisor and mentor, Dr. Irv Binik. His wisdom, wit and willingness to let me explore new technologies have been instrumental in building my love of research and crucial to teaching me the immense positive impact that a great supervisor can have on an individual’s development. I want to thank you, Irv, for your incredible support over the years- you have made this journey so worthwhile and I count myself lucky to be among the many

“Irvivors” that scatter the globe! I would also like to extend my gratitude to Dr.

Serge Carrier, whose passion for research, clinical expertise and resourcefulness were essential in implementing the thermography studies.

Thank you so much, Serge, for all the time and energy that you have devoted and for being such a fantastic mentor.

In addition, I would like to thank Rhonda Amsel, whose statistical knowledge was crucial to these studies and whose love of teaching has greatly inspired my career; Dr. Samir Khalifé for laying the foundation for this research; and to Francine Bouvier and Janet Bradley for all their help with the ultrasound study. To Natalie Cartwright, Shiri Freiwald, Yun Gao, Ariella

Kleiman, Katherine Muldoon, Louise Overington, Clio Pitula, Natalie Stratton,

Anton Van Hamel, Christina Yager and Arieyu Zhang, I thank you immensely

for the countless hours that you spent cleaning data, conducting screenings and testing participants.

I would also like to extend my gratitude towards my current and former labmates Dr. Caroline Pukall, Dr. Nicole Flory, Dr. Kimberley Payne, Marie-

Andree Lahaie, Alina Kao, Melissa Farmer, Laurel Paterson, Seth Davis and

Sabina Sarin for their continued feedback, as well as their incredible emotional support, humour and friendship over these years. In addition, I would like to thank my dearest friends Dr. Yvonne Blonde, Stephanie Riddell and Alexandra Yarrow for always cheering me on.

Above all, I would like to dedicate this thesis and give thanks to my family: first, to my parents, Soili and Erkki, for their incredible love and encouragement throughout the years- I would not have achieved my goals without their guidance; to my siblings Tuomas and Tiina, for always bringing a smile to my face when I needed it most; to Natasha, Victor, Olesya and

Babushka Zina, you are the most fantastic and loving in-laws; and most of all to my husband, Tim, you give me the strength, confidence and love to continue forward through life’s challenges.

This research was made possible through the generosity of Seahorse

Biosciences for the thermography equipment, my doctoral fellowship from the

Fonds pour la Recherche en Santé du Québec, an operating grant to Dr.

Binik from the Canadian Institutes of Health Research, and grants to Drs.

Binik and Carrier from Pfizer and the Canadian Male Sexual Health Council.

INTRODUCTION

Sexual psychophysiology is a growing discipline that has expanded our understanding of human sexual response. There are, however, several important limitations with the instruments used to quantify sexual arousal that, to date, have not been adequately addressed (Janssen,

2001). These limitations with measurement could be contributing to a number of ongoing research issues such as the discordance between physiological and subjective sexual responses in women (Chivers, Seto,

Lalumière, Laan, & Grimbos, 2010), the differences in sexual responding between men and women (Laan & Janssen, 2007) and the lack of clear physiological indicators of normative versus dysfunctional sexual response in women (Graham, 2010).

The following literature review highlights the primary limitations with the psychophysiological measurement of sexual arousal that served as a starting point for this dissertation. In reviewing the literature, it is clear that there is a need for empirically validated instrumentation that can be used for both sexes and in research and clinical settings. As such, the first manuscript in this dissertation, entitled “Convergent and discriminant validity of clitoral color Doppler ultrasonography as a physiological measure of female sexual arousal”, published in the Journal of Sex and

Marital Therapy, 32, pp.281-287, examined the use of ultrasound to record genital vasocongestion in women. Ultrasonography had been established

as a clinical tool to assess sexual functioning in men (Wilkins, Sriprasad, &

Sidhu, 2003; Connoly, Boriakchanyavat, & Sue, 1996) and had also been applied to the study of female sexual response (e.g., Garcia et al., 2005), however, important methodological issues had not yet been addressed.

As such, the goal of this paper was to examine the discriminant validity of ultrasound in women as well as to examine the relationship between ultrasound measures and subjective reports of sexual arousal, both of which were lacking in the current literature.

Based on the results of this research, it was determined that there were significant limitations with ultrasonographic measurement in women, which led to the next manuscript of the dissertation entitled

“Thermography as a physiological measure of sexual arousal in both men and women”, published in the Journal of Sexual Medicine, 4, pp. 93-105.

The primary objective of this paper was to be the first publication examining the modern thermographic camera as an instrument to measure sexual response. Specifically, the goals were to examine the discriminant validity of thermography as a measure of sexual arousal in men and women, to examine the relationship between thermographic output and subjective sexual arousal in men and women and to determine whether thermography can be used to directly compare male and female sexual responses.

The promising results from this initial study were then followed up in the final manuscript of this dissertation entitled “An examination of the validity of thermography as a physiological measure of sexual arousal in a non-university adult sample”, to be published in the August 2010 issue of the Archives of Sexual Behavior (doi: 10.1007/s 10508-009-9496-4). The goals of this paper were to generalize the results from the previous study to an older sample of participants, to further examine the discriminant validity by adding an anxiety control condition, and to examine the within- subject relationship between continuous physiological and subjective sexual arousal recording.

References

Chivers, M., L., Seto, M. C., Lalumière, M. L., Laan, E., & Grimbos, T.

(2010). Agreement of self-reported and genital measures of sexual

arousal in men and women: A meta-analysis. Archives of Sexual

Behavior, 39, 5-56.

Connoly, J. A., Boriakchanyavat, S., & Lue, T. F. (1996). Ultrasound

evaluation of the penis in the assessment of impotence. Journal of

Clinical Ultrasound, 24, 481-486.

Garcia, S., Talakoub, L., Maitland, S., Dennis, A., Goldstein, I., &

Munarriz, R. (2005). Genital duplex Doppler ultrasonography before

and after sexual stimulation in women with sexual dysfunction: Gray

scale, volumetric, and hemodynamic findings. Fertility and Sterility,

83, 995-999.

Graham, C. A. (2010). The DSM diagnostic criteria for female sexual

arousal disorder. Archives of Sexual Behavior, 39, 240-255.

Janssen, E. (2001). The psychophysiology of sexual arousal. In M. W.

Weiderman & B. E. Whitley (Eds.), Handbook for conducting

research on human sexuality (pp. 131-171). Mahwah, NJ:

Erlbaum.

Laan, E., & Janssen, E. (2007). How do men and women feel?

Determinants of subjective experience of sexual arousal. In E.

Janssen (Ed.), The psychophysiology of sex (pp.278-290).

Bloomington, IN: Indiana University Press.

Wilkins, C. J., Sriprasad, S., & Sidhu, P. S. (2003). Colour Doppler

ultrasound of the penis. Clinical Radiology, 58, 514-523.

LITERATURE REVIEW

The systematic study of human sexual response dates back to the late 19th and early 20th centuries with Robert Latou Dickinson and his observation of intravaginal changes during sexual arousal in women

(Rosen & Beck, 1988). While Dickinson pioneered the use of instrumentation to observe changes in the body during sexual response, it was the work of Masters and Johnson that brought sexual psychophysiology to the forefront with their book entitled Human Sexual

Response (1966). Masters and Johnson recruited almost 700 individuals to partake in their laboratory studies of sexual arousal. By filming individuals and couples engaged in sexual activity, and by using physiological monitoring devices, Masters and Johnson were able to describe peripheral indicators of sexual arousal in men and women, such as genital vasocongestion. From their observations, they developed a model of sexual responding that involved four phases: excitement, plateau, orgasm and resolution, which has become the basis for the classification of sexual dysfunctions in the Diagnostic and statistical manual of mental disorders (DSM-IV-TR, American Psychiatric

Association, 2001) and has guided research programs in the psychophysiological measurement of sexual arousal for over four decades.

Since the work of Masters and Johnson, a variety of instruments have been developed to record the physiological indicators of sexual arousal in men and women, with the primary focus being the measurement of genital changes. Although extra-genital measures, such as skin conductance and heart rate variability have also been measured, these responses are not as specific to sexual arousal and, thus, have not been adopted as primary indicators of sexual response (Zuckerman, 1971; see Rosen & Beck, 1988, for a review of non-genital measures of sexual arousal). Additionally, due to the physiological differences in male and female genital anatomy, the majority of sexual psychophysiology instruments are specific to either men or women, though there are four less widely used ones that can be applied to both sexes.

Specific to men, the recording of sexual response has focused on changes in penile volume, circumference, rigidity and blood flow (see

Janssen, 2001 and Rosen & Beck, 1988, for review of instruments). The measurement of penile volume has been achieved through the use of volumetric plethysmography, whereby changes in penile volume are measured through air displacement (Freund, 1963). For this device, the penis is inserted through a rubber ring into an inflatable tube encased in a glass cylinder that is subsequently inflated with air (Freund, 1963). Penile circumference measures, or penile strain gauges, are less cumbersome than the volumetric devices and involve a ring that is placed around the penis, which records increased resistance with increases in penile 7

circumference (e.g., Fisher, Gross & Zuch, 1965). Penile rigidity has been measured through the Rigiscan Monitor, which consists of two loops placed at the base and shaft of the penis that tighten at pre-set intervals, providing a measure of force during erection (Bradley, 1985). Finally, penile blood flow has been measured through photoplethysmography, whereby a light-emitting diode is attached to the dorsal midline of the penis (Bancroft & Bell, 1985).

In women, the measurement of sexual response has focused on intra-vaginal changes as well as blood flow measurement to the labia and clitoris (see Janssen, 2001 and Rosen & Beck, 1988, for review of instruments). The most widely-used instrument is the vaginal photoplethysmograph, a tampon-shaped device that is inserted into the vagina to measure changes in vaginal blood flow through light reflectance

(Sintchak & Geer, 1975; Hoon, Wincze, & Hoon, 1976). In addition to this device, the heated oxygen electrode has been used to measure vaginal vasocongestion via a heated electrode that is placed on the vaginal wall with a suction device (Levin, 2006). More recently, the labial photoplethysmograph, a device that clips on to the labia to record blood flow (Prause, Cerny & Janssen, 2005); and serial magnetic resonance imaging (MRI), which measures relative blood volume to the clitoris

(Heiman & Maravilla, 2007), have been described for the assessment of sexual arousal in women.

The vast majority of sexual psychophysiology studies have used the sex-specific instrumentation described above, with vaginal photoplethysmography and penile strain gauges being the most commonly used devices. All of these methods of measurement have important limitations that could be confounding our understanding of human sexual arousal. Firstly, the use of different instruments with differing outputs and scales for men and women has made it difficult to interpret the comparisons in sexual responding between the sexes. So, although there is a literature suggesting that men have greater specificity in their sexual responses than women (Chivers, Seto, & Blanchard, 2007; Steinman,

Wincze, Sakheim, Barlow, & Mavissakalian, 1981; Suchinsky, Lalumière,

& Chivers, 2009), that men are better able to estimate genital change than women (Heiman, 1977; Laan & Janssen, 2007), and that men have a stronger concordance between physiological and self-report measures of sexual arousal than women (Chivers, Seto, Lalumière, & Grimbos, 2010), it is not clear to what extent these results could be influenced by the use of different instruments.

Additionally, quantitative limitations such as relative output scales, high within-subject variability, the lack of standardized calibration protocols and standardized data reduction has made it difficult to conduct between- groups comparisons of sexual arousal, as well limit the degree to which within-subject comparisons can be made (Janssen, 2001; Prause, Cerny

& Janssen, 2005; Prause & Janssen, 2006; Rosen & Beck, 1988). These 9

particular limitations have had a significant effect on the study of female sexual dysfunction, where, to date, there are no definable physiological markers of impaired sexual arousal (Graham, 2010). While a number of studies have been conducted to compare sexually healthy women to those complaining of arousal difficulties, physiological sexual responses have not differentiated the groups (Meston & Gorzalka, 1996; Morokoff &

Heiman, 1980; Rellini & Meston, 2006; Wincze et al., 1976).

Finally, particular instrument limitations such as the sensitivity to movement artifacts or menstruation, as well as the intrusiveness of the measures, can restrict research designs. For example, intra-vaginal instruments cannot be used to study sexual response during menstruation due to the potential interference that the blood can have on readings

(Prause & Janssen, 2006). Additionally, devices that are sensitive to participant movement, such as the vaginal photoplethysmograph or pelvic

MRI, cannot be used to examine genital response across higher intensities of sexual arousal such as orgasm (Heiman & Maravilla, 2007; Prause &

Janssen). Furthermore, research designs that require genital stimulation pose a problem for most instruments as the devices themselves need to remain firmly fixed on the genitals during recording.

One way to address the limitations of more widely used sex specific instruments is to examine technologies that can be applied to both men and women. At present, there exist four different measurement devices

that can be used for both sexes: anal electromyography, genital temperature measurement through thermistors and thermographic cameras and blood flow measurement through Doppler ultrasonography.

Anal electromyography involves the use of a small probe that is inserted into the anus to measure muscle contractions during sexual arousal (Bohlen & Held, 1979). Initial studies of this instrument during sexual arousal demonstrated its applicability to both men and women, however, it is possible that the perceived intrusiveness of the device limited its popularity as a measure of sexual arousal (Bohlen & Held, 1979;

Bohlen, Held, & Olwen Sanderson, 1980; Bohlen, Held, Olwen Sanderson,

& Ahlgren, 1982). Additionally, although the anal probe can be used to record contractions during orgasm, these anal contractions did not correlate with subjective reports of sexual arousal or subjective indicators of the time of orgasm (Bohlen et al., 1980).

Genital temperature measurement has also been examined for the study of sexual arousal in both men and women through the attachment of thermistors to the penis or labia (Fisher, Gross, & Zuch, 1965; Henson,

Rubin, Henson, & Williams, 1977), or by measuring remotely with a thermographic camera (Seeley, Ambramson, Perry, Rothblatt, & Seeley,

1980). Early studies show increases in genital temperature during sexual arousal for both men and women and concordance between physiological and self-report measures (Fisher, Gross & Zuch, 1965; Henson & Rubin,

1978; Henson, Rubin, Henson & Williams, 1977; Slob, Ernste & van der

Werff ten Bosch, 1991; Slob, Koster, Radder & van der Werff ten Bosch,

1990; Solnick & Birren, 1977; Webster & Hammer, 1983). Reports of slow latency to baseline, however, have made this methodology unpopular in research that often uses multiple stimuli within one session (Payne &

Binik, 2006).

The final technology that has been used for both men and women is Doppler ultrasound. This instrument has been used primarily for the study of sexual dysfunction in men (e.g., Connoly, Boriakchanyavat, &

Lue, 1996), however, there are a number of reports assessing clitoral blood flow in women (Bechara et al., 2003; Bechara, Bertolino, Casabé,

Fredotovich, 2004; Becher, Bechara, & Casabé, 2001; Garcia et al., 2005;

Khalifé, Binik, Cohen, & Amsel, 2000; Munarriz, Maitland, Garcia,

Talakoub, & Goldstein, 2003). While there have been reports of increased blood flow to the clitoris using mechanical means and vasoactive agents, the discriminant and concurrent validity of this measure have not been established. In theory, Doppler ultrasonography provides advantages over more widely used instruments as the same instrument can be used for both men and women and it provides a direct measure of blood flow to the genitalia. In addition, for women, the measurement of blood flow to the clitoris, the female homologue of the penis, makes more theoretical sense than recording sexual response in the vaginal walls (Levin, 2007).

Although there is agreement that the most popular instruments for the measurement of physiological sexual response have significant methodological and theoretical limitations, they continue to be used

(Janssen, 2001; Rosen & Beck, 1988). This leads to several important problems, including the impact of instrumentation artifact on research results and interpretation. Alternative measurement tools have been suggested over the years, however, they have not caught on for various reasons. It is possible that the perceived intrusiveness of some measures, the limitations imposed on research designs, as well as the limited evidence of validity and clinical applicability could be hindering the widespread use of instruments that are not sex specific. Taking these considerations into account, as well as the difficulties with more widely used instruments, the goal of this dissertation was to examine and provide validity to measurement technologies that could address the existing limitations in sexual psychophysiology and to provide a tool that could be easily interpreted and adopted to measure sexual arousal in men and women. What follows are the results of three studies, the first examining ultrasonography and the other two examining thermography as physiological measures of sexual arousal.

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Behavior, 39, 5-56.

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CONVERGENT AND DISCRIMINANT VALIDITY OF CLITORAL

COLOR DOPPLER ULTRASONOGRAPHY AS A MEASURE OF

FEMALE SEXUAL AROUSAL

Published in the Journal of Sex and Marital Therapy

Reference:

Kukkonen T.M., Paterson, L., Binik, Y. M., Amsel, R., Bouvier, F., &

Khalife, S. (2006). Convergent and Discriminant validity of clitoral color

Doppler ultrasonography as a measure of female sexual arousal. Journal of Sex and Marital Therapy, 32, 281-287.

Abstract

The convergent and discriminant validity of clitoral ultrasonography as a measure of female sexual arousal was examined by assessing the following: a) its ability to discriminate between sexual and other forms of arousal; b) its correlation with subjective ratings of arousal. Results from

63 healthy pre-menopausal women indicate that ultrasonography was not successful in differentiating sexual arousal from a humor control condition.

Furthermore, there was no correlation between clitoral blood flow measures and subjective sexual arousal. Additional research is required to establish the specificity of ultrasonography as a measure of sexual arousal.

Introduction

Clitoral ultrasonography has recently been suggested as a possible replacement for the standard vaginal photoplethysmography used in most physiological studies of female sexual arousal. An early study of clitoral ultrasonography demonstrated that it is possible for two independent ultrasonographers to reliably assess clitoral blood flow in women who are not sexually aroused (Khalifé, Binik, Cohen, & Amsel, 2000).

Subsequently, other studies have demonstrated differences in clitoral ultrasound measures in response to a variety of stimuli related to sexual functioning. Bechara and colleagues have reported significant differences in clitoral hemodynamics after the topical or sublingual introduction of vasoactive agents (Bechara, Bertolino, Casabé, Fredotovich, 2004;

Becher, Bechara, & Casabé, 2001). They also reported differential ultrasound readings in women with sexual dysfunction from healthy controls (Bechara, Bertolino, Casabé, Munarriz, Goldstein, Morin, et al.,

2003). Munarriz, Maitland, Garcia, Talakoub and Goldstein (2003) have shown increased blood flow through ultrasonography after EROS therapy; and, most recently, Garcia, Talakoub, Maitland, Dennis, Goldstein, and

Munnariz (2005) have reported volumetric and hemodynamic changes in the clitoris following video and vibratory sexual stimulation for women with sexual dysfunctions.

In principle, clitoral ultrasonography is a more direct measure of the physiology underlying female sexual arousal than vaginal 25

photoplethysmography; it also allows for direct comparison with men, where ultrasonography has become the gold standard for assessment of erectile difficulties (Wilkins, Sriprasad, & Sidhu, 2003; Connoly,

Boriakchanyavat, & Sue, 1996). Further validation of clitoral ultrasonography would require at least two types of evaluation: 1. the discriminant validity, i.e., does it differentiate sexual arousal from other forms of arousal; 2. convergent validity, i.e., does it correlate with subjectively rated sexual arousal.

The following study compared clitoral blood flow across three conditions: sexual arousal, positive-emotion arousal (humor), and neutral.

In addition, we examined the correlation between clitoral blood flow and subjective reports of sexual arousal. Despite the fact that previous research on female sexual arousal has controlled for general physiological arousal by inducing negative emotional states such as anger or fear, we used humor because recent research and theorizing has indicated that positive emotions such as humor may elicit a more similar psychophysiological reaction to sexual arousal than do negative emotions

(Fry, 2002).

Materials and Methods

This experiment was reviewed and approved by the McGill University

Faculty of Medicine Institutional Review Board.

Participants

Healthy pre-menopausal women between the ages of 18 to 45 years were eligible to participate. Exclusion criteria consisted of any medication use that interferes with sexual arousal, a history of any sexual arousal difficulties or sexual dysfunction, menopause, major medical and/or psychiatric illness, or current pregnancy or breastfeeding.

Experimental Manipulation

Volunteer participants were randomly assigned to one of three experimental conditions (sexual arousal, humor or neutral). Four separate seven-minute film segments were used as stimuli: 1) a neutral baseline video, consisting of a travelogue of the Amazon (Day, Cook, & Wolfe,

2001); 2) a sexually arousing video, consisting of an erotic film clip validated to induce sexual arousal in women at the Kinsey Institute

(Janssen, Carpenter, Graham, 2003); 3) a humorous video, consisting of two separate segments of The Best Bits of Mr. Bean (Vertue, Davies,

Birkin, & Weiland, 1999); and 4) a neutral video, consisting of a travelogue of Madagascar (Day et al., 2001). Olympus Eyetrek FMD-250W goggles connected to a laptop computer were used to display the videos privately to each participant.

Measures

Clitoral Blood Flow

An Aloka 5000 ultrasound machine and a 13 mhz linear probe were used to measure clitoral blood flow. The following ultrasound parameters were recorded: peak systolic velocity (PSV), peak diastolic velocity (PDV) and resistance index (RI). A female ultrasound technician, one of the investigators (FB), took all blood flow measurements at the junction of the crura and the body of the clitoris, following the procedure described by

Khalifé et al. (2000).

Subjective Arousal

Subjective arousal was assessed by a female research assistant with a series of Likert-style questions on sexual arousal, humor and relaxation, with response options ranging from 0 (not at all) to 10 (the most ever).

Procedure

After a brief semi-structured interview to collect sociodemographic, basic health and sexual health information, women were accompanied to the ultrasound room and shown the equipment. Participants undressed from the waist down, assumed the lithotomy position on the examination table and covered themselves with a disposable towel.

Clitoral blood flow was first measured before the experiment began.

All participants then viewed the same neutral baseline video, followed by either the sexually arousing, humorous, or neutral video. Clitoral blood

flow and subjective arousal were measured immediately after both the baseline and experimental videos.

Data Analysis

All ultrasound measures were log transformed to normalize the variation in their distribution. Differences between groups were analyzed using univariate ANOVAs with post-hoc Tukey tests. For analysis of the experimental condition, the baseline measures served as covariates. All correlations were measured through Pearson’s method.

Results

Sample Characteristics

Sixty-three women participated in the study: 21 in the sexual arousal condition, 22 in the humor condition, and 20 in the neutral condition. There were no significant group differences with respect to age

(M = 25.78 years, SD = 5.99), primary language, occupation, years of education, place of birth, relationship status, sexual orientation, birth control method or phase of menstrual cycle.

Subjective Measures of Sexual Arousal

There were no significant group differences for subjective ratings of arousal during the baseline neutral film. During the experimental condition, however, subjective ratings clearly differentiated the groups, with women in the sexual arousal group rating their video as significantly

more sexually arousing (sexual arousal M = 6.00, SD = 2.55; humor M =

.77, SD = 2.16; neutral M = .40, SD = 1.19), and women in the humor group rating their video as significantly more humorous than those in the other two groups (humor M = 6.05, SD= 3.08; neutral M= 1.10, SD = 1.74; sexual arousal M = 2.48, SD = 2.46). Ratings of relaxation did not differ significantly across the three groups.

Ultrasound Measures of Sexual Arousal

Similar to the subjective measures, there were no significant group differences in baseline ultrasound measures. In the experimental condition, there was a significant difference in mean PSV (F (2, 62) = 4.99, p = 0.02) between the sexual arousal and neutral groups, with women who viewed the sexually arousing video having a higher mean PSV (M = 10.36,

SD = 5.17) than those who viewed the neutral video (M = 6.32, SD =

2.36). Women who viewed the humorous video did not differ significantly on PSV from either of the other two groups (M = 9.36, SD = 8.05). The other ultrasound measures, PDV and RI, did not significantly differentiate the three groups (see Table 1).

Correlation Between Subjective and Physiological Measures

There were no significant correlations between clitoral blood flow and subjective sexual arousal measures during the experimental condition

(range r = .009 to .179, p > .05).

Discussion

The two goals of this study were to establish whether increases in clitoral blood flow as measured by ultrasonography are specific to sexual arousal and whether they are correlated with subjective sexual arousal.

While ultrasonography clearly differentiated the sexual arousal condition from the neutral condition, it failed to discriminate between sexual arousal and another positive emotional state, humor. In addition, no measure of clitoral blood flow was significantly correlated with subjective sexual arousal.

There are several methodological considerations that may affect these conclusions. First, as clitoral ultrasonography depends on the free- hand placement and manipulation of an ultrasound probe on the clitoris, it is possible that ultrasonographer technique affected our results. Although two different ultrasonographers can reliably measure clitoral blood flow in healthy women who are not sexually aroused (Khalifé et al., 2000), it is less clear whether this reliability extends to experimental manipulations of sexual arousal. The pressure with which the probe is applied to the clitoris, in addition to the manipulation required to obtain an ultrasound reading, could inadvertently increase blood flow when coupled with a positive emotional state such as humor. The use of a remote-controlled ultrasound probe, which would standardize application pressure and angle of measurement, eliminate any effects of technician presence and allow for continuous measurement, might reduce the clitoral blood flow increases that accompanied general physiological arousal in this study.

Second, as we did not use mechanical or pharmacological agents to obtain sexual arousal, our reported ultrasound measures were substantially lower than those of other studies. It may be the ultrasonography is less sensitive than vaginal photoplethysmography in its ability to discriminate between different forms of arousal. This would limit its clinical application.

Third, while subjective ratings clearly differentiated the three groups, there were no significant correlations between the women’s self- reported sexual arousal and measures of clitoral blood flow. This also occurs with vaginal photoplethysmography. A common explanation for this type of discordance has been that women are complex and that their physiological sexual arousal does not reliably translate into mental sexual arousal. In our study, the women were clearly mentally sexually aroused and physiologically there were increases in PSV from baseline, but it may be that the considerable variability in PSV among participants resulted in a lack of correlation with subjective ratings. In addition, the relatively modest overall PSV increase (a difference of 2.33 cm/sec. in mean PSV from baseline to erotic) may not be sufficient to obtain significant correlations with subjective ratings of sexual arousal. As no other published studies of clitoral blood flow have correlated subjective with physiological measures, it is hard to determine whether or not our results are typical of clitoral ultrasonographic research in general. Future studies

should certainly incorporate measures of subjective sexual arousal to further examine this phenomenon.

With some methodological modifications, clitoral ultrasound could be a promising measure of female sexual arousal. Before it can be advanced as a sound research and clinical instrument, however, its validity must be established.

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Table 1. Mean clitoral hemodynamics during experimental condition

Experimental Condition

Neutral Humor Erotic

PSV 6.32 (2.86) 9.36 (8.05) 10.36 (5.17)*

PDV 1.44 (.74) 3.28 (8.54) 2.18 (1.58)

RI .76 (.10) .82 (.10) .80 (.11)

* p < .05

TRANSITIONAL TEXT 1

Results from the previous study demonstrated the limitations of using clitoral ultrasound as a measure of sexual arousal. While numerous studies have reported increases in blood flow to the clitoris following mechanical or pharmacological stimulation, none had examined whether these blood flow changes were specific to sexual response or whether the obtained measurements correlated with subjective report. We found no significant relationship between physiological and subjective sexual arousal and there were no significant differences in the clitoral peak systolic velocity (PSV) of participants in the sexual arousal and humour conditions. Additionally, the other measures obtained, end diastolic velocity (EDV) and the resistance index (RI), failed to differentiate participants in the sexual arousal condition from those in the control conditions. One of the primary limitations of this study is its intrusiveness because the requirement of a technician to physically manipulate the ultrasound probe on the clitoris could be disrupting to the process of sexual arousal. Furthermore, the single recording of physiological measures following the presentation of stimuli does not provide an indication of change over time and may not accurately represent a participant’s response during a sexual stimulus. Although ultrasonography provides a direct measure of blood flow and can be used for men and women, we felt that the limitations with the methodology, in addition to the non-significant relationship between ultrasound measures and women’s 38

self-report of sexual arousal, would significantly impede the adoption of this device in research and clinical settings.

A measurement technology that could theoretically address these limitations, in addition to those present with other instruments, is that of thermography. Thermography uses infrared radiation to detect temperature and, as such, could provide an indirect measure of genital blood flow through temperature change. The following potential advantages over existing instruments prompted us to conduct the next study on the feasibility of using thermography to study sexual arousal in men and women: 1) thermography does not require any physical contact with participants and can be remotely controlled; 2) it can provide a continuous recording of temperature; 3) it can theoretically be used for both men and women because there is no genital manipulation required.

THERMOGRAPHY AS A PHYSIOLOGICAL MEASURE OF SEXUAL

AROUSAL IN BOTH MEN AND WOMEN

Published in the Journal of Sexual Medicine

Reference:

Kukkonen, T. M., Binik, Y. M., Amsel, R., & Carrier, S. (2007).

Thermography as a physiological measure of sexual arousal in both men and women. Journal of Sexual Medicine, 4, 93-105.

Abstract

Introduction: Current physiological measures of sexual arousal are intrusive, hard to compare between genders and quantitatively problematic. Aim: To investigate thermal imaging technology as a means of solving these problems. Methods: Twenty-eight healthy men and thirty healthy women viewed a neutral film clip after which they were randomly assigned to view one of three other video conditions: 1) neutral (n = 19); 2) humor (n = 19); 3) sexually explicit (n = 20). Main Outcome Measures:

Genital and thigh temperatures were continuously recorded using a TSA

ImagIR camera. Subjective measures of sexual arousal, humor and relaxation were assessed using Likert-style questions prior to showing the baseline video and following each film. Results: Statistical (Tukey HSD) post-hoc comparisons (p < .05) demonstrated that both men and women viewing the sexually arousing video had significantly greater genital temperature (m = 33.89 °C, sd = 1.00) than those in the humor (m = 32.09

°C, sd = 0.93) or neutral (m = 32.13 °C, sd = 1.24) conditions. Men and women in the erotic condition did not differ from each other in time to peak genital temperature (men m = 664.6 sec., sd = 164.99; women m = 743 sec., sd = 137.87). Furthermore, genital temperature was significantly and highly correlated with subjective ratings of sexual arousal (range r = 0.51 to 0.68, p < .001). There were no significant differences in thigh temperature between groups. Conclusion: Thermal imaging is a

promising technology for the assessment of physiological sexual arousal in both men and women.

Introduction

A variety of instruments have been introduced to measure the physiological markers of sexual arousal in men and women. For men, these include penile plethysmography, rigiscan monitoring and penile ultrasonography; for women, vaginal photoplethysmography has become the gold standard but pelvic MRI, labial thermistors and photoplethysmography, clitoral ultrasonography and the heated oxygen electrodes have also been used (See Janssen 2001 for a review; Prause,

Cerny & Janssen, 2005).

Each of the above-mentioned technologies has significant limitations. Perhaps most important is the fact that none can be used for both men and women. While an anal probe capable of measuring vascular and muscular activity during sexual arousal for both genders does exist, it remains relatively rarely used in research and, to our knowledge, has not been employed to compare male and female sexual response (Bohlen & Held, 1979; Bohlen, Held & Olwen Sanderson, 1980;

Bohlen, Held, Olwen Sanderson & Ahlgren, 1982). The lack of parallel measurement with the most widely used instruments leaves open the possibility that reported differences in sexual arousal between men and women may be the result of technological rather than actual gender differences. Furthermore, it is also possible that the reported lower correlations between physiological and subjective measures of sexual arousal in women as opposed to men may be the result of instrumentation 43

artifacts. It is also a possibility, however, that the lower correlations between physiological and subjective arousal in women are due to inadequate methodology and statistical analyses as shown by Rellini and colleagues (Rellini, McCall, Randall & Meston, 2005).

All of the above mentioned devices to measure sexual arousal are potentially intrusive and require genital contact or insertion, either by the participant or an experimenter. This intrusiveness is likely to affect the actual experience of arousal in a variety of ways for different participants

(Kukkonen et al., 2006; Prause, Cerny & Janssen, 2005).

Less obvious are the quantitative difficulties in interpreting the data from existing measures. For example, data derived from vaginal and labial photoplethysmography, as well as penile plethysmography have no absolute measurement scale and are therefore difficult to interpret between subjects (Janssen, 2001; Prause et al., 2005; Prause & Janssen,

2006). Moreover, in the case of penile plethysmography and rigiscan monitoring, it is not clear how closely the output measures correlate with clinical criterion of penile rigidity (Janssen, 2001). This quantitative problem makes it difficult to use current measures to establish diagnostic criteria, which require between subjects comparability and standardization.

It is also the case with women that none of the established measures of physiological sexual arousal have been reliably used to determine diagnostic criteria for female sexual arousal difficulties. For example,

recent attempts to establish the validity of vaginal photoplethysmography in discriminating women with genital sexual arousal disorder from controls has yielded mixed results (Brotto, Basson & Gorzalka, 2004; Rellini &

Meston, 2006).

Normal anatomical variation may also interact with these other problems. For example, penile size differences cannot be easily calibrated between subjects using penile plethysmography or rigiscan monitoring (Udelson et al., 1998; Wespes & Schulman, 1984). Internal penile anatomical differences can lead to the misinterpretation of ultrasound differences (Sakamoto, Nagata, Saito, Okumura & Yoshida,

2004). For women, naturally occurring differences in the length of the vagina can result in positioning differences for vaginal probes used in plethysmography (Gillan & Brindley, 1979). These vaginal length differences may further be accentuated by sexual arousal, which is thought to affect the length of the vaginal barrel (Rosen & Beck, 1988).

While it is standard procedure in vaginal photoplethysmography to have a plastic stopper attached to the vaginal probe to control for the length of insertion, subject movement is a known artifact and is likely to be accentuated by the experience of sexual arousal (Prause & Janssen,

2006). Though the heated oxygen electrode appears to be less influenced by anatomical variation than the vaginal photoplethysmograph, it cannot be used for long periods of time due to the damage it can cause to the vaginal walls (Levin, 2006). 45

Current thermal imaging technology has the capability to address the methodological problems mentioned above in the following ways: 1) it can be used for both men and women; 2) it does not require genital contact; 3) it provides an absolute temperature measure. The two basic principles upon which this technology works are as follows: 1) human skin or various membranes constantly emit electrochemical energy, such as infrared radiation, and are very efficient radiators of such energy; 2) it is possible to detect infrared emission from the skin by remote sensing.

While these principles have been known for some time, a convenient technology to implement them was not available until the 1990s when high-resolution, fast scanning cameras became readily available. This new equipment can produce thermal images where the average temperature of less than a millimeter of skin can be determined with a precision of .07 ˚C in a very short period of time. Thermographic imaging is now being used in numerous medical diagnostic situations including dermatology (e.g., detection of lesions & inflammatory conditions), rheumatology (inflammation and blood flow in fibromyalgia, scleroderma,

& rhematoid arthritis), breast cancer detection, and surgery (detection of blood flow changes; Di Carlo, 1995; Ecker et al., 2002; Martini et al., 2002;

Parisky et al., 2003; Szabo et al., 2000). With respect to sexual arousal, genital temperature is hypothesized to be directly related to the physiological mechanisms of sexual arousal, i.e., increased blood flow.

An earlier type of thermographic technology (UTI-

SPECTROTHERM LWIR) was used in the 1980s to measure sexual arousal (Abramson & Pearsall, 1983; Abramson, Perry, Rothblatt, Seeley

& Seeley, 1981; Abramson, Perry, Seeley, Seeley & Rothblatt, 1981;

Seeley, Abramson, Perry, Rothblatt & Seeley, 1980). Although these studies included only a relatively small number of participants in one laboratory and the quantitative capacity of the thermography of the time was limited, the results were quite promising. Genital temperature increase in both men and women appeared to be specific to sexual arousal induction and was highly correlated with subjective self-report.

There are also several reports of non-thermographic surface thermistor genital temperature measurements as an index of sexual arousal in both women and men (Fisher, Gross & Zuch, 1965; Henson &

Rubin, 1978; Henson, Rubin, Henson & Williams, 1977; Payne & Binik,

2006; Slob, Ernste & van der Werff ten Bosch, 1991; Slob, Koster, Radder

& van der Werff ten Bosch, 1990; Solnick & Birren, 1977; Webster &

Hammer, 1983). Similar to early research with thermography, results from these studies demonstrate increases in labial and penile temperature during exposure to erotic stimuli. Furthermore, these temperature increases correlated well with subjective ratings of arousal.

The present research was designed to assess the feasibility of using current thermal imaging technology as a measure of sexual arousal

in healthy men and women by recording and comparing penile and labial temperature during a sexual arousal condition, a positive mood inducing arousal condition and a neutral condition. Most previous research (see

Kukkonen et al., 2006 and Redouté et al., 2000 for exceptions) attempted to distinguish sexual arousal from general physiological arousal by using control groups experiencing negative mood inductions such as anger or fear. A positive emotional state, humor, was chosen as the control for this study because research and theory indicates that humor may better represent a similar psychophysiological reaction in the body to sexual arousal than negative emotional states (Fry, 2002). This would be particularly true in non sexually dysfunctional populations, and would thus serve as a better control for general arousal.

We hypothesized that penile and labial temperature, as measured through a thermal imaging camera, would significantly differentiate the sexual arousal condition from the humor and neutral conditions, with the sexual arousal condition demonstrating higher genital temperatures than the other two conditions. In addition, we predicted that genital temperature would significantly correlate with subjective ratings of sexual arousal for both men and women and that both sexes would show similar patterns of temperature change consistent with the traditional Master’s and Johnson model of the sexual response cycle (Masters & Johnson,

1966).

Materials and Methods

The experiment was reviewed and approved by the McGill

University Faculty of Medicine Institutional Review Board; we obtained written informed consent from each participant.

Participants

Potential participants were recruited through university advertisements. Healthy males and females between the ages of 18 to 40 years were eligible to participate, however, our final sample consisted of

60 English speaking, heterosexual individuals ranging in age from 18-28 years. Two men failed to reach a stable baseline temperature and were thus excluded from the analysis, leaving us with a total of 58 participants:

19 in the neutral condition, 19 in the humor condition and 20 in the erotic condition. An additional 13 potential participants were excluded from the experiment for the following reasons: 2 could not be matched with existing participants; 1 moved away before a testing session could be scheduled; 7 were not eligible due to the medications they were taking; 1 reported difficulties with sexual arousal; and 2 had difficulties with sexual arousal and were also taking medication. Our exclusion criteria consisted of the absence of intercourse experience, never having seen pornography, a history of sexual arousal difficulties or sexual dysfunction of any kind, any medication use that interferes with sexual arousal, or major medical and/or

psychiatric illness. Participants were reimbursed $50 CDN to cover expenses related to their participation in this study.

Experimental Manipulation

Participants were matched in groups of 6 (3 men and 3 women) for age

(+/- 3 years), as well as oral contraceptive use in women, and then randomly assigned to one of three experimental conditions (neutral, humor or sexual arousal). All women were tested during the follicular phase of the menstrual cycle to control for the possible effects of the menstrual cycle on sexual arousal. The follicular phase was estimated by testing women within 12 days of the start day of their menstruation, but only once bleeding had ended. Six separate 15 minute film segments were used as stimuli. Two of these segments were shown to all participants and included the following: 1) a neutral video segment that consisted of still images of nature accompanied by calming music to allow for body temperature to stabilize; 2) a baseline video segment which consisted of a travelogue of the Yukon and Alaska (LaBarge, 2002; Glusic, 1994). The other video clips were viewed for the experimental manipulation and included the following: 1) the neutral control condition that consisted of a travelogue of the Amazon; 2) a humor control video which was comprised of three separate segments of The Best Bits of Mr. Bean; 3 & 4) a male oriented erotic film clip validated at the Kinsey Institute and a female oriented one based on criteria deemed to be sexually arousing to women

(Day, Cook & Wolfe, 2001; Vertue, Davies, Birkin & Weiland, 1999;

Janssen, Carpenter & Graham, 2003).

Equipment A TSA ImagIR thermal imaging system provided by Seahorse

Bioscience (North Billerica, MA) was used to monitor genital temperature.

The sampling interval was set at eight frames per second for this experiment. The sensitivity of this camera is 0.07˚C. For men, the camera was placed 1.0m diagonally left from the participant, at a height of

1.09m, angled at 30 degrees. For women, the camera was situated directly facing the examination table at a distance of 0.5m, at a height of

1.09m and angled at 20 degrees. The slight differences in camera placement was necessary to have a clear image of the genital region for men and women. If the camera were to be placed directly facing the examination table for men as with women then, as erection occurs, the tip of the penis would obstruct the view of the rest of the penis.

Olympus eyetrek FMD-250W goggles, connected to a DVD player and laptop computer through a switchbox, were used to display the videos and subjective questionnaires privately to each participant. A standard intercom was used for communication between the participant and female investigator, who was in the adjoining room.

Background Information

Demographic information was collected from each participant using open-ended questions concerning age, place of birth, mother tongue, 51

occupational status and years of schooling. A question on current relationship status (which of the following best describes your current dating/couple/marital situation) included the following response options: no regular partner at the moment; dating one partner regularly; dating more than one partner; living with a partner; married; separated/divorced; widowed; other- explain. Basic health/ medical history included the following: 1) are you currently taking any medications- if yes which ones, and what dosage; 2) are you suffering from any chronic illnesses, e.g., diabetes, hypertension- if yes, which ones; 3) have you had a gynecological exam in the past year- if no, why not; 4) have you ever been to see a urologist- if yes, why; 5) when was the start day of your last period; 6) have you experienced childbirth- if yes, how many children.

Basic sexual health information included the following questions: 1) are you primarily heterosexual, gay or bisexual; 2) do you currently suffer from any sexual problems; 3) have you ever watched a sexually explicit video or movie; 4) do you feel uncomfortable about or object to the idea of watching a sexually explicit video or movie; 5) do you have any difficulty getting aroused at sexually explicit videos or movies; 6) do you have any difficulty getting aroused by yourself (e.g., masturbation); 7) are you concerned over your ability to get sexually aroused- if yes, would you like a referral. Questions two to seven had the following response options: yes, no, or I don’t know. For those questions that were answered with a

yes or I don’t know, participants were prompted to elaborate on their answers.

Outcome Measures

Genital Temperature

Genital temperature was assessed through a region of interest situated on the shaft of the penis for men and on the left labia majora for women. A non-genital temperature control was continuously monitored on the inner right thigh of all participants.

Subjective Arousal

Subjective arousal was assessed with a series of separate Likert- style questions. Questions on relaxation (overall, how relaxed did you feel during this film), enjoyment (overall, how much did you enjoy the film), humor (overall, how funny did you find the film) and sexual arousal

(overall, how sexually aroused did you become during this film; how would you rate your peak sexual arousal; overall, how sexually aroused were you mentally during this film; did watching the video make you feel like having sex with a partner; did watching the video make you feel like masturbating; overall, how sexually aroused were you physically during this film; how much genital change did you feel during this film; how much lubrication did you feel during this film and how much genital tingling or fullness did you feel during this film ( for women); how would you rate your erection in response to this film - men) had response options ranging from 0 (not at

all) to 10 (the most ever). A question on when peak sexual arousal occurred (at what point during the film would you say that you were most sexually aroused) included the following response options: 1) was not at all sexually aroused; 2) within the first 5 minutes; 3) between 5-10 minutes; 4) during the last 5 minutes; 5) varied throughout; 6) other

(explain). A question on comparison of sexual arousal (how sexually aroused did you feel during the film as compared to how sexually aroused you typically are with a partner) ranged from –5 (much less sexually aroused) to +5 (much more sexually aroused), with 0 indicating no difference from with a partner. Finally, questions regarding the influence of the camera on arousal were included (did the process of having your genitals filmed affect you in any way (Yes- describe or No); did it increase or decrease sexual arousal and to what extent 0 (not at all) to 10 (the most possible); did it increase or decrease how funny you thought the film was, and to what extent; did it increase or decrease how relaxed you felt during the video, and to what extent).

Procedure

After a telephone screening, participants arrived at the laboratory where the study procedures and equipment were explained again and informed signed consent was obtained. A brief semi-structured interview was conducted to collect sociodemographic and basic health and sexual health information. Once the female experimenter left the room,

participants were instructed to get undressed from the waist down, and men were asked to sit on the examining table with their legs apart whereas women were asked to assume the lithotomy position. All participants were instructed to put on the DVD goggles to view the videos.

The thermal imaging camera recorded temperature for the duration of the experiment and was focused on the penis and an area of the inner thigh of the right leg for men, and the labia majora and inner right thigh for women.

Ambient room temperature was monitored for each participant and maintained constant with less than one degree Centigrade variation within each testing session. The first 15 minute neutral video segment was used to allow for skin temperature to adjust and to stabilize with the room temperature. Within this 15 minute period, all but two of the men achieved the required three minute period of stable temperature allowing them to progress to the next stage of the experiment. For men, stable temperature required a change of less than 0.5 °C over three minutes whereas for women, the criteria was more stringent, requiring a change of less than

0.05 °C over a three minute period. Differences in required temperature stabilization reflect the smaller degree of temperature change expected from women due to the proximity of the labia to the body as compared to the penis, which can cool down to a greater degree. Following temperature stabilization, participants answered questions on subjective arousal. Immediately following the questionnaire, all participants were shown another 15 minute neutral travelogue which served as the baseline

measure of their temperature. Subjective ratings of arousal were obtained once more through the questionnaire upon completion of the video. The final video sequence presented was either the sexually arousing video, the humorous film or another neutral travelogue followed again by questions on subjective arousal. Once all three videos were viewed, participants were instructed to remove the goggles and to get dressed at their convenience. The investigator then met with each participant to discuss the study and answer any additional questions.

Data Analysis

In order to assess differences in genital temperature, a three-way

ANOVA with one repeated factor was conducted on average genital temperature between minutes 5 and 10 of each film. The middle 5 minutes of temperature was used to minimize possible carry over effects from the previous film and to give a more conservative and stable measure of genital temperature change by avoiding the highest temperatures recorded towards the end of the erotic condition. The independent variables for the analysis were gender (male or female), experimental condition (neutral, humor or erotic) and time of genital temperature recording as the repeated factor (baseline versus experimental). In addition, to examine patterns of sexual arousal, we assessed time to peak genital temperature during the experimental condition with a univariate ANCOVA where gender and experimental

condition were used as the independent variables and baseline time to peak temperature as a covariate. Finally, a three-way ANOVA with one repeated factor was conducted on average thigh temperature between minutes 5 and 10 of each film to determine whether temperature differences were specific to the genital region. Differences between groups on subjective ratings of arousal were measured using MANOVAs.

All significant results were further assessed using tests of simple main effects and Tukey HSD Post Hoc tests. Pearson’s correlations between each subjective arousal measure and genital temperature were calculated by taking the difference scores between baseline average genital temperature for the middle 5 minutes of recording and experimental condition average genital temperature for the middle 5 minutes of testing

(time period 2) and correlating that with the differences scores of the 11 questions on subjective arousal. As our subjective arousal questions do not specifically ask participants to respond regarding their arousal during the middle 5 minutes of the film, additional correlational analyses were carried out using subjective arousal difference scores and the following 3 time points to determine if there were notable differences in correlations when different time points were used: 1) average genital temperature difference scores for the first 5 minutes of baseline and experimental films

(time period 1); 2) average genital temperature differences scores for the last 5 minutes of baseline and experimental films (time period 3); 3) overall average genital temperature difference scores for the whole 15 minutes of

baseline and experimental films (time period 4). In order to compare correlations between men and women, correlations were transformed to

Fisher’s z. Finally, a principal components analysis with varimax rotation for significant factors was conducted to determine if the 11 questions measuring subjective arousal could be reduced to a smaller number of factors. Using Kaiser’s rule, factors were only considered significant if they had eigenvalues over 1. In addition, a factor was considered reliable only if it had four or more variable loadings above .6. Pearson’s correlations were then conducted between reliable factors and the 4 time periods for genital temperature in order to examine whether our correlations of the 11 individual questions of subjective arousal and genital temperature remain consistent while using factor scores.

Results

Sample Characteristics

Fifty-eight participants were included in our final analyses: 19 in the neutral condition, 19 in the humor condition and 20 in the erotic condition.

There were no significant differences between experimental groups with regards to age (M = 21.16 years, SD = 2.11), education (range = 13-19 years, M = 15.36 years, SD = 1.35), place of birth (86.2% North America), or relationship status (43.1% single, 51.7% dating, 5.2% cohabiting/married). Sixty percent of women were using oral contraceptives and all were nulliparous. None of the participants were

virgins and all of them had previous experience viewing pornographic videos. Finally, none of the participants reported any difficulties with sexual arousal.

Subjective Measures of Arousal

Changes in subjective arousal from baseline to experimental condition were measured through difference scores. MANOVA analysis of difference scores indicated significant differences among film groups on various ratings of arousal, which were further assessed by univariate

ANOVAs. Participants in the erotic condition found their video to be significantly less relaxing (m = -1.85, sd = 2.08) than those in the neutral

2 condition (m = 0.32, sd = 2.11) (F (2, 52) = 5.09, p = .01, ηp = .16).

Individuals in the humor condition did not report significant differences in relaxation from either of the other two groups (m = -0.32, sd = 2.81). All three film conditions differed significantly from each other in reported

2 humor level of the film (F (2, 52) = 31.05, p < .001, ηp = .54), with participants in the humor condition rating their film as the funniest (m =

4.84, sd = 2.14), followed by the erotic (m = 2.9, sd = 2.61) and then neutral (m = -0.42, sd = 1.39) conditions. All questions on subjective sexual arousal significantly differentiated the erotic condition from the two control conditions (see Table 1). The only significant difference between men and women was that women overall experienced a greater decrease in relaxation from baseline to experimental condition (m = -1.43, sd = 2.13)

2 than men (m = 0.21, sd = 2.60) (F (1, 52) = 8.31, p = .006, ηp = .14).

Finally, there was one gender (male/female) x film (neutral/humor/erotic)

2 interaction concerning desire to masturbate (F (2, 52) = 3.26, p = .046, ηp

= .11), where men experienced a greater decrease in desire to masturbate from baseline following the humorous film (m = -1.0, sd = 1.33) than women (m = -0.1, sd = 0.88).

When asked if the process of recording their genitals affected their sexual arousal, 55% of the participants in the erotic condition responded that it decreased their arousal while 20% and 25% said that it increased and had no effect on their arousal respectively. Participant reports of intrusiveness or sexually enhancing effects of the thermographic recording for each condition are reported in Table 2.

Measure of Non-Genital Control Temperature

A three-way ANOVA with one repeated factor for average thigh temperature did not reveal any significant interactions between time of recording (baseline/experimental) x gender (male/female) (F (1, 52) =

0.70, p = .41), time of recording x film condition (neutral/humor/erotic) (F

(2, 52) = 0.38, p = .69) or time of recording x gender x film condition (F (2,

52) = 0.03, p = .97) (see figure 1).

Physiological Measures of Sexual Arousal

The three-way ANOVA with one repeated factor for average genital temperature during time period 2 (middle 5 minutes) revealed significant interactions with respect to time of recording (baseline/experimental) x

2 gender (male/female) (F (1, 52) = 8.12, p = .006, ηp = .14), time of

recording (baseline/experimental) x film condition (neutral/humor/erotic) (F

2 (2, 52) = 30.05, p < .001, ηp = .54), and time of recording x gender x film

2 condition (F (2, 52) = 6.99, p = .002, ηp = .21). The univariate ANCOVA for time to peak temperature with baseline time to peak temperature as a covariate revealed a significant difference in film conditions (F (2, 51) =

2 30.46, p < .001, ηp = .54), as well as a gender x film condition interaction

2 (F (2, 51) = 3.42, p = .041, ηp = .12). The comparison of time to peak temperature between genders was not significant (F (1, 51) = 3.64, p =

.062).

Comparison of Genital Temperature Across Film Conditions

Using simple main effects wherever significant interactions were found, we determined that there were no significant differences among film conditions (neutral, humor and erotic) at baseline for average genital temperature (p = .16). Similarly, there were no significant differences in time to peak temperature at baseline (p = .14). During the experimental recording, however, significant differences in average genital temperature

2 were detected (p < .001, ηp = .40). Specifically, participants in the erotic condition showed significantly greater average genital temperatures (m =

33.89 °C, sd = 1.0) than those in the humor (m = 32.09 °C, sd = .93) or neutral (m = 32.13 °C, sd = 1.24) control groups, who did not differ from each other (see Figure 1). Furthermore, participants in the erotic condition had significantly longer time to peak temperature (m = 703.8 seconds, sd

= 153.35) than either the neutral (m = 355.63 seconds, sd = 284.44) or

2 humor control conditions (m = 197.89 seconds, sd = 198.58) (p < .001, ηp

= .54).

Comparison of Genital Temperature Across Men and Women

Tests of simple main effects revealed that, when comparing genital temperature between men and women irrespective of film condition, women had significantly higher baseline genital temperature (m = 32.63

2 °C, sd = 0.71) than men (m = 31.86 °C, sd = 1.74) (p = 0.03, ηp = .08).

Women also had significantly shorter time to peak temperature during baseline (m = 287.9 seconds, sd = 290.07) than men (m = 483.75

2 seconds, sd = 296.02) (p = .014, ηp = .11). These differences are no longer present during the experimental recording where men and women, averaged across film groups, did not differ significantly from each other with regards to average genital temperature (p = 0.4) or time to peak temperature (p = .06). Due to the differences in baseline genital temperature between men and women, baseline temperature was included as a covariate for the following analyses of simple main effects.

Within each film group, only men and women in the erotic condition differed significantly from each other during experimental recording in that men had significantly higher average genital temperature (m = 34.47 °C,

2 sd = 0.84) than women (m = 33.3 °C, sd = 0.81) (p = 0.021, ηp = .28).

While genital temperatures differed between men and women in the erotic condition, both sexes recorded similar patterns of genital arousal in that average length of time to peak genital temperature did not differ between

men (m = 664.6 seconds, sd = 164.99) and women (m = 743 seconds, sd

= 137.87) in the erotic condition, using baseline time to peak temperature as a covariate (p = .41). While there were also no differences in time to peak genital temperature between men and women in the humor control group (men m = 258.22 seconds, sd = 228.95; women m = 143.6 seconds, sd = 159.25), a significant difference in time to peak temperature was found for men and women in the neutral control condition (men m =

499.11 seconds, sd = 305.08; women m = 226.5 seconds, sd = 199.91) (p

2 = .031, ηp = .24), with men taking a greater amount of time to reach their peak temperature than women. The general pattern of temperature change in each of the three experimental conditions is similar for men and women despite differences in time to peak temperature for the neutral condition, as illustrated in figures 2 & 3, which show the temperature graphs for each participant.

Correlation Between Subjective and Physiological Measures

To examine the relationship between genital temperature and subjective ratings of arousal, correlational analysis was performed using

Pearson’s method on the difference scores of subjective ratings of arousal and the difference scores from baseline to experimental condition for average genital temperature for the first 5 minutes (time period 1), middle

5 minutes (time period 2), last 5 minutes (time period 3) and for the entire

15 minutes (time period 4) of recording. Each measure of subjective arousal (e.g., overall sexual arousal, peak sexual arousal, etc.) was

significantly positively related to each genital temperature measure (period

1 range r = 0.34 - 0.52, p < .01; period 2 range r = 0.51 to 0.68, p < .001; period 3 range r = 0.57 – 0.71, p < .001; period 4 range r = 0.46 – 0.61, p

< .001). Using Fisher’s transformation, we determined that there were no significant differences in correlations of subjective and physiological arousal between men and women using average genital temperature difference scores of the middle 5 minutes of each condition (range z = -.14 to 1.12, p = .13 to .45), last 5 minutes of each condition (range z = -.11 to

.98, p = .16 to .46) and overall 15 minutes of each condition (range z = -

.06 to 1.08, p = .14 to .20). While all of the male ratings of subjective sexual arousal were significantly positively correlated with the average genital temperature difference score during the first 5 minutes of baseline and experimental conditions (time period 1) (range r = .48 - .68, p < .01), only one female rating of subjective sexual arousal, genital tingling, was significantly correlated with genital temperature during this period (r = .37, p < .05).

To further examine the relationship between genital temperature and subjective ratings of arousal, a principal components analysis with varimax rotation was conducted on the difference scores for the 11 subjective arousal questions. Only one reliable factor consisting of all eight of the sexual arousal questions emerged with a range in factor scores of 3.96, with -1.51 as a minimum score and 2.45 as a maximum. A second factor consisting of the humor and enjoyment questions was not

considered reliable as it had only two variables with significant loadings

(the question on relaxation did not load significantly on either of these two factors). Similar to the individual questions correlations, the sexual arousal factor was significantly positively correlated with genital temperature during period 1 (r = .50, p <.001), period 2 (r = .67, p < .001), period 3 (r = .71, p < .001) and period 4 (r = .62, p < .001). In addition, the only difference between men and women was again that women’s subjective sexual arousal was not correlated with genital temperature during period 1 (first 5 minutes of testing).

Discussion

Thermal imaging is a promising tool for the physiological assessment of sexual arousal. Results from this first study indicate that thermal imaging can clearly differentiate sexual arousal from humor and neutral conditions in healthy young men and women. Participants in the sexually arousing condition experienced an average increase of 2.08 ˚C in genital temperature from baseline in response to the erotic film, whereas participants in the neutral and humor conditions experienced relatively stable genital temperatures from baseline to experimental condition

(decreases of 0.24˚C and 0.53˚C respectively). In contrast to genital temperature change during sexual arousal, thigh temperature remained stable for all three conditions throughout testing, suggesting that increases in temperature during sexual arousal are centered in the genital region.

Furthermore, the increases in genital temperature were significantly

associated with increases in subjective ratings of sexual arousal, providing support for the physiological measure of genital temperature corresponding to the subjective experience of sexual arousal. The clarity of the results is such that one can simply look at a participant’s temperature graph to determine whether or not they were in the erotic condition. This type of “eyeball data” is a relative rarity in psychophysiological research and suggests the further development of this methodology is worthwhile.

What is also striking about these results are the similarities between men and women. Both men and women in the erotic condition had significantly higher genital temperatures than men and women in the neutral and humor conditions. While men had greater increases in genital temperature (M = 3.3 ˚C) than women ( M = 0.86 ˚C), women started off with significantly higher baseline genital temperature (M = 32.63˚C) than men (M = 31.86 ˚C). The proximity of the labia to the body compared to that of the shaft of the penis is likely to account for this difference. In addition, the dorsal artery of the penis, which runs through the shaft, would likely increase temperature to a greater extent than any of the capillaries located throughout the labia majora, thus potentially accounting for the higher temperatures recorded in men.

Our results suggest there are no differences between men and women in length of time to peak sexual arousal during the erotic condition.

Men averaged 11 minutes 5 seconds to recorded peak genital temperature, whereas women had an average of 12 minutes 23 seconds.

Though showing men and women different videos introduces the possibility that the similarities in time to peak temperature are an artifact of differing visual stimuli, research suggests that showing the same video may not be ecologically valid (Janssen, Carpenter & Graham, 2003).

Indeed, examining the graphs of all participants visually demonstrates similar patterns of temperature change for men and women in the erotic condition when gender appropriate videos are used. Furthermore, the erotic condition for both genders can be clearly distinguished from the relatively stable temperature graphs for participants in the two control conditions (see figures 2 & 3). The differences in time to peak temperature between the sexes during baseline and for the neutral control condition is likely due to the increased variability of temperature in men.

Whereas women’s labial temperature remains fairly stable in neutral conditions (again due to the proximity of the labia to the body), men’s penile temperature tends to vary more, creating a situation where peak temperature might take longer to reach. In examining the standard deviations of time to peak temperature, men appear to have more variation in the neutral and humor conditions; men’s standard deviations for time to peak temperature were 305.1 seconds and 229 seconds respectively, whereas for women, the standard deviations for neutral and humor control videos were 199.9 and 159.2 seconds respectively.

The similarities between men and women are also present in their subjective ratings of sexual arousal. There is some evidence which suggests that women are able to indicate levels of genital arousal that correlate with physiological measures, however, in most previous research, women’s physiological and subjective reports of sexual arousal have been poorly correlated, if at all (Brotto & Gorzalka, 2002; Laan &

Janssen, In Press; Rellini et al., 2005). Though we cannot say for sure whether the process of having a camera filming their genitals directed women to be more aware of vascular changes in the genital region, the

DVD goggles block external stimuli and make it unlikely that there would be more focus on the genitals than with other available measures.

The poor correlations between subjective and physiological sexual arousal in women from previous research has led to the suggestion that women are not as adept at detecting physiological differences in their bodies as men are and that women are more highly influenced by cognitive and emotional factors than men (Laan & Janssen, In Press). In addition, recent research comparing male and female sexual arousal suggests that women’s sexual arousal is non-specific and fundamentally different from men’s (Chivers, 2005). While it was not a goal of this study to examine these theories, the overall similar correlations between physiological and subjective sexual arousal in men and women certainly introduces the possibility that disparities in male and female sexual arousal could be due in part to measurement or instrumentation error 68

rather than to true differences. The one time period in this study in which women’s physiological and subjective arousal was not consistently correlated was when we averaged the temperature recorded during the first five minutes of the experimental condition and correlated it with reported subjective arousal. It may be that our method of averaging the first five minutes is not sensitive enough for the lower levels of temperature change experienced in the beginning of the condition. It is also possible that a continuous measure of subjective arousal, like that of

Rellini and colleagues (2005) would be more sensitive to detecting a relationship between these measures at early stages of arousal.

The most obvious disadvantage of thermal imaging technology is its cost. Equipment similar to what we have used is advertised on the

Internet at prices ranging from 55 000 USD to 100 000 USD. While this technology is less intrusive than others in that it requires no genital contact, roughly half of our participants indicated that having a camera film their genitals did influence their subjective sexual arousal. Unfortunately, most previous research, except for that of Prause and colleagues (2005), does not report whether participants find the methodology used intrusive, and we are not aware of other studies except for our own that have investigated the sexually enhancing effects of measuring arousal

(Kukkonen et al., 2006). As thermography does not require genital contact, however, it is likely better suited than other technologies for women suffering from dyspareunia and vaginismus. 69

Another limitation of this technology is that there is no standardized method for examining the data. Following testing, we checked each recorded data frame for each participant to ensure that the genital region of interest we were monitoring (an area on the labia majora and shaft of the penis) was the same throughout. This is necessary because the subject may move during the experiment to find a more comfortable position or his/her genitalia may move as a result of sexual arousal. Any movement required us to manually reposition the thermography’s “region of interest” on the data image after the actual monitoring session is over.

This manual repositioning is a standard feature of the currently available technology but it is impossible to insure exactly the same location. It is unlikely, however, that genital location errors of 10-15mm would seriously affect our data. A more serious issue might be how to measure analogous genital structures in men and women. For example, clitoral temperature could only be measured if the external genitalia were held open.

Although temperature provides a known interval scale that can be used to compare men and women, this does not mean that a two degree change in women is directly equivalent to a two degree change in men. In addition, while there is a certain degree of variability between subjects, body temperature is a tightly regulated system that should produce very little variability within one participant measured repeatedly in the same condition. Indeed, examining the data from our neutral control condition provides initial support for the stability of genital temperature within

participants. This presumed consistency within a condition, as well as a sensitivity to change if a new condition is introduced, would make genital temperature a reliable measure of sexual arousal. While we have demonstrated a sensitivity to change in genital temperature and have some support for its stability, further research is required to establish the degree of variability within participants measured repeatedly in the same condition as well as how to translate temperature change between genders.

Previous research measuring genital temperature has suggested that this measure has a slow return to baseline (Payne & Binik, 2006).

Unfortunately, we did not measure this in the current study. We also do not know whether genital temperature can differentiate between genital blood flow and pooling. Finally, it is crucial using this technology to control variations in genital temperature resulting from external factors such as room temperature or internal factors such as menstrual cycle effects

Conclusion

Our research is consistent with but improves upon older thermography research and previous surface thermistor genital temperature research (Abramson & Pearsall, 1983, Abramson, Perry,

Rothblatt, et al., 1981; Abramson, Perry, Seeley, et al., 1981; Seeley et al.,

1980; Fisher et al., 1965; Henson & Rubin, 1978; Henson et al., 1977;

Slob et al., 1991; Slob et al., 1990; Solnick & Birren, 1977; Webster &

Hammer, 1983; Payne & Binik, 2006). With present equipment we were 71

able to continuously and remotely monitor a specific area and show that sexual arousal is differentiable from neutral and positive mood induced states, and that temperature increases during sexual arousal are specific to the genital region when compared to a control area on the thigh. While one previous study has recorded temperature changes in the pectoral region during sexual arousal, we did not measure this area and cannot confirm whether this is the case (Abramson & Pearsall, 1983).

Thermography is a promising technology for the measurement of physiological sexual arousal. Future research should replicate these findings with older participants and also demonstrate that thermography can differentiate sexual arousal from arousal induced by negative emotional states. Additionally, determining the ranges of temperature associated with no arousal and high sexual arousal, as well as better understanding the between and within subject variability of temperature would be useful for mapping human sexual response. If such research is successful, then we believe that thermography should be tested with clinical populations to determine its discriminant validity and suitability as a diagnostic tool for male and female sexual arousal disorder.

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Table 1. Means and Standard Deviations of Difference Scores for Subjective

Ratings of Sexual Arousal

Question Erotic Humor Neutral ηp²

Desire to have sex with 5.15 (2.62) -0.32 (1.42) -0.58 (1.07) .70 partner*

Desire to masturbate* 5.10 (2.24) -0.53 (1.17) -0.32 (0.75) .77

Overall sexual arousal* 4.60 (1.67) 0.11 (1.29) -0.21 (0.71) .76

Peak sexual arousal* 4.55 (2.06) 0.05 (1.72) -0.37 (0.68) .68

Physical sexual arousal* 4.30 (1.56) -0.16 (1.07) -0.58 (0.69) .80

Perception of genital 4.00 (1.89) -0.21 (1.69) -0.21 (0.71) .65 change*

Mental sexual arousal* 3.80 (2.29) -0.32 (1.67) -0.53 (0.91) .60

Comparison of current 2.35 (1.53) -0.26 (1.1) -0.16 (0.38) .56 arousal to that with a partner*

*p<0.0001

Table 2. Percentage of Participants Who Indicated That Having a Camera

Film Their Genitals Increased, Decreased or Did Not Affect Their Sexual

Arousal.

Increase Decrease No Effect

Baseline 36.2% (N = 21) 12.1% (N = 7) 51.7% (N = 30)

Experimental

Neutral 21.0% (n = 4) 15.8% (n = 3) 63.2% (n = 12)

Humor 31.6% (n = 6) 15.8% (n = 3) 52.6% (n = 10)

Erotic 20.0% (n = 4) 55.0% (n = 11) 25.0% (n = 5)

35 Neutral (genital) Neutral (thigh) Humor (genital) 34 Humor (thigh) Erotic (genital) Erotic (thigh) 33

Temperature (Degree Centigrade) (Degree Temperature 29 Baseline Experimental Time of Recording

Figure 1. Mean genital (solid line) and thigh (dotted line) temperature

during baseline and experimental recording for Neutral (n = 19), Humor (n

= 19), and Erotic (n = 20) groups.

Erotic Conditon: Females Humor Condition: Females Neutral Condition: Females

36 36 36 35 35 35

34 34 34 33 33 33 32 32 32 31 31 31 30 30 30 29 29 29 Temperature 28 28 28 27 27 27 (DegreeCentigrade) 26 26 26 1 201 401 601 801 1001 1201 1401 1601 1801 1 201 401 601 801 1001 1201 1401 1601 1801 1 201 401 601 801 1001 1201 1401 1601 1801

Time (seconds)

Figure 2. Graphs illustrating labial temperature in degrees Celsius for

all female participants in erotic (n = 10), humor (n =10) and neutral

(n= 10) conditions over baseline and experimental conditions.

Erotic Condition: Males Humor Condition: Males Neutral Condition: Males

36 36 36 35 35 35

34 34 34 33 33 33 32 32 32 31 31 31 30 30 30

29 29 29 28 28

Temperature 28

27 27 27

(DegreeCentigrade) 26 26 26 1 201 401 601 801 1001 1201 1401 1601 1801 1 201 401 601 801 1001 1201 1401 1601 1801 1 201 401 601 801 1001 1201 1401 1601 1801

Time (seconds)

Figure 3. Graphs illustrating penile temperature in degrees Celsius

for all male participants in erotic (n = 10), humor (n =9) and neutral (n

= 9) conditions over baseline and experimental conditions.

TRANSITIONAL TEXT 2

Results from the first published study using modern thermographic

cameras were promising. It is possible to detect and differentiate sexual

arousal from control conditions using a thermographic camera. In

addition, the temperature changes were specific to the genitals and

significantly correlated with self-reported sexual arousal for both men and women. While this first study provides support for the use of thermography as a measure of sexual arousal, our study was limited in

certain ways: 1) the sample of participants were relatively young (mean

age 21 years) and were not necessarily representative of a more general

population; 2) while a pleasant arousal control stimulus makes intuitive

sense, the majority of sexual psychophysiology studies use control stimuli

that provoke negative emotions such as anxiety or fear; 3) while a self-

report questionnaire at the end of the stimuli provides information on a

participant’s overall experience, a continuous measure of subjective

sexual arousal would allow us to further examine the within-subject

relationship between physiological and subjective sexual arousal and

provide an indicator of change in subjective sexual arousal over time.

These limitations prompted the next study entitled “An evaluation of the

validity of thermography as a physiological measure of sexual arousal in a

non-university adult sample”.

AN EVALUATION OF THE VALIDITY OF THERMOGRAPHY AS A

PHYSIOLOGICAL MEASURE OF SEXUAL AROUSAL IN A NON-

UNIVERSITY ADULT SAMPLE

In Press in the Archives of Sexual Behavior

(DOI 10.1007/s10508-009-9496-4)

Reference:

Kukkonen, T. M., Binik, Y. M., Amsel, R., & Carrier, S. (2010). An evaluation of the validity of thermography as a physiological measure of sexual arousal in a non-university adult sample. Archives of Sexual

Behavior, 39.

Abstract

Thermography is a promising technology for the physiological

measurement of sexual arousal in both men and women. This study was

designed to 1) generalize our previous college student thermography

study findings to an older sample (M age = 37.05 years); 2) add an anxiety

control group to further examine the specificity of temperature change;

and 3) examine the relationship between genital temperature and a

continuous measure of subjective sexual arousal. Healthy men (n = 40) and women (n = 39) viewed a neutral film clip after which they were randomly assigned to view one of four other videos: neutral (n = 20),

humor (n = 19), anxiety provoking (n = 20) or sexually explicit (n = 20).

Genital and thigh temperature were continuously recorded using a TSA

ImagIR thermographic camera. Continuous and discrete reports of

subjective sexual arousal were also obtained. Results support the validity

of thermography as a measure of sexual arousal: temperature change

was specific to the genitals during the sexual arousal condition and was

significantly correlated with subjective continuous and discrete reports of

sexual arousal. Further development should assess the potential of

thermography as a tool for the diagnosis and treatment evaluation of

sexual arousal difficulties and for studying gender differences.

Introduction

Thermography has been shown to be a promising technology for the physiological measurement of sexual arousal in both men and women

(Kukkonen, Binik, Amsel, & Carrier, 2007). This technology works on the principle that all matter emits infrared radiation at a level proportional to its temperature. Current thermographic cameras can remotely detect this radiation and provide a continuous temperature reading of the object in focus with an accuracy of 0.07 °C. As increased genital blood flow is a marker of sexual arousal, a thermographic camera can indirectly track vasocongestion by measuring changes in genital temperature.

Thermography provides numerous potential advantages over existing instrumentation (for a review of current instrument validity, see

Janssen, 2001): (1) thermography does not require any genital manipulation or contact, which may result in either discomfort or in some cases arousal (Kukkonen et al., 2006; Prause, Cerny, & Janssen, 2005);

(2) the same instrumentation can be used for both men and women; and

(3) thermographic output, temperature, is measured on a known absolute scale, allowing for between group comparisons.

Thermographic cameras were used in the 1980s to measure sexual arousal; however, these cameras were technologically limited in that the temperature measurement had a large margin of error, the cameras could not provide continuous measurement, and were restricted to measuring temperature in one pre-determined area (Abramson & Pearsall, 1983; 89

Abramson, Perry, Rothblatt, Seeley, & Seeley, 1981; Abramson, Perry,

Seeley, Seeley, & Rothblatt, 1981; Seeley, Abramson, Perry, Rothblatt, &

Seeley, 1980). Over the past 15 years, these problems have been solved

and modern variants have been deployed in numerous medical diagnostic

situations (Di Carlo, 1995; Ecker et al., 2002; Martini et al., 2002; Parisky

et al., 2003; Szabo et al., 2000).

In a first study using modern thermographic cameras to record

sexual arousal, we continuously monitored genital and thigh temperature

in 58 healthy young men and women (M age = 21.16 years) who were

randomly assigned to either a sexual arousal, a positive mood inducing

arousal condition (humor) or a neutral control condition (Kukkonen et al.,

2007). The results indicated that thermal imaging clearly differentiated the

sexual arousal condition from the two control conditions, with the camera

recording an average increase in genital temperature of 1.75 °C during

sexual arousal (increases of 3.3 °C and 0.86 °C for men and women,

respectively). Furthermore, there were no significant changes in the non-

genital control area, the thigh, indicating that temperature increases were

specific to the genital region. Finally, increases in genital temperature

were significantly and positively correlated with subjective ratings of

sexual arousal (range r = .51-.68), and men and women showed similar patterns of temperature change overall, as measured through latency to maximal physiological arousal.

While the results from this first thermographic study were quite promising and provide initial support for the discriminant and convergent validity of thermography as a measure of sexual arousal, there were limitations: (1) our sample consisted of healthy undergraduate students and, as such, the results do not indicate the applicability of this instrument for older populations and clinical settings (external validity); (2) there was no anxiety control condition, which has been the most commonly used stimulus for evaluating the discriminant validity of instruments measuring sexual response (e.g., Both, Everaerd, & Laan, 2003; Laan, Everaerd, &

Evers, 1995; Prause et al., 2005); and (3) there was no continuous monitoring of sexual arousal, which provides an indication of concurrent validity and is also one way to examine individual differences in arousal

(Brody, 2007; Laan et al., 1995; Laan, Everaerd, van der Velde, & Geer,

1995; Mitchell, DiBartolo, Brown, & Barlow, 1998; Rellini, McCall, Randall,

& Meston, 2005; Wincze, Hoon, & Hoon, 1977; Wincze, Venditti, Barlow,

& Mavissakalian, 1980).

To correct these problems and further examine the validity of thermography as a measure of sexual arousal, the present study assessed sexual arousal in 79 30-45 year old healthy men and women by remotely recording penile and labial temperature via thermography during a sexual arousal condition, a neutral control condition, a positive mood inducing arousal condition (humor), and an anxiety inducing arousal condition. In addition, a continuous measure of subjective arousal was

used to examine the relationship between subjective and physiological sexual arousal. We hypothesized that, similar to the 18-28 year olds, the

30-45 year old participants would demonstrate increases in temperature that were specific to the sexual arousal condition and to the genital region.

Furthermore, we predicted that genital temperature would be significantly correlated with both the continuous and discrete subjective measures of sexual arousal. Finally, we predicted that men and women would show similar patterns of overall temperature change.

Method

Participants

Potential participants were recruited through online and newspaper advertisements. Healthy males and pre-menopausal females between the ages of 30 to 45 years were eligible to participate. In total, 39 women and

40 men took part (M age = 37.05 years, SD = 4.20). The majority of our sample was of North American origin (59.5%), the remainder identified themselves as either European (15.2%) or from other areas of the world

(25.3%; e.g., Asia, Middle East, South and Middle America, Caribbean,

Africa). Participants were primarily English speaking (68.4%; French speaking 31.6%) and occupational status varied, with 36.7% of participants identifying as professionals, 27.8% as students, 20.3% working in the service industry, and 15.2% indicating other. The mean

years of schooling was 17.08 (SD = 0.41) with men having significantly more schooling than women, t(77) = 2.37, p < .05; men M = 18 years, SD

= 3.93; women M = 16.13, SD = 3.01. Forty-three percent of participants were cohabiting or married, 32.9% were dating one or more partners, 19% were single, and 5.1% indicated that they were divorced or separated.

None of the women were taking oral contraceptives and 66.7% of them were nulliparous.

An additional 21 potential participants were excluded upon telephone screening based on the following criteria: absence of intercourse experience (0 participants), never having seen pornography (4 participants), a history of sexual arousal difficulties or sexual dysfunction of any kind (5 participants), any medication use that interfered with sexual arousal (6 participants), any current major medical and/or psychiatric illness (1 participant), or indication that the menopausal transition had begun (5 participants).

Participants were reimbursed $50 CDN to cover expenses related to their participation in this study.

Measures

Experimental Design and Manipulation

Participants were matched in groups of 8 (4 men and 4 women) for age (+/- 3 years), as well as parity in women, and then randomly assigned to one of four experimental conditions (neutral, humor, anxiety or sexual 93

arousal), until there was a total of 10 men and 10 women in each film condition. All women were tested during the follicular phase of the menstrual cycle to control for the possible effects of the menstrual cycle on sexual arousal. The follicular phase was estimated by testing women within 12 days of the start day of their menstruation, but only once bleeding had ended (M cycle day during testing = day 9). Seven separate audiovisual 15-minute film segments were used as stimuli. Two of these segments were shown to all participants and included the following: (1) a neutral video segment that consisted of still images of nature accompanied by calming music to allow for body temperature to stabilize

(LaBarge, 2002); (2) a baseline video segment which consisted of a travelogue of the Yukon and Alaska (Glusic, 1994). The other video clips were viewed as part of the experimental manipulation and included the following: (1) a neutral control condition that consisted of a travelogue of the Amazon (Day, Cook, & Wolfe, 2001); (2) a humor control video which was comprised of three separate segments of The Best Bits of Mr. Bean

(Vertue, Davies, Birkin, & Weiland, 1999); (3) an anxiety control video depicting a mother and her child being attacked by a rabid dog (Blatt &

Singer, 1983); (4 and 5) separate male and female oriented erotic film clips depicting consenting adults engaging in a variety of sexual activities, such as manual and oral genital stimulation and penile vaginal intercourse

(see Janssen, Carpenter, & Graham, 2003).

Equipment A TSA ImagIR thermal imaging system provided by Seahorse

Bioscience (North Billerica, MA) was used to monitor genital temperature.

The sampling interval was set at eight frames per second. The sensitivity of this camera was 0.07 ˚C and it had an operating range from 15 °C –40

°C. For men, the camera was placed 1.0 m diagonally left from the participant, at a height of 1.09 m, angled at approximately 30 degrees. For women, the camera was situated directly facing the examination table at a distance of 0.5 m, at a height of 1.09 m and angled at approximately 20 degrees. The camera is not required to be at any specific distance from participants, though greater proximity allows for a more detailed image, and the slight differences in camera placement were necessary to have a clear image of the genital region for men and women. If the camera were to be placed directly facing the examination table for men as with women then, as erection occurred, the tip of the penis would obstruct the view of the rest of the penis.

I-O display systems i-theater goggles (Sacramento, CA), connected to a DVD player and laptop computer through a switchbox, were used to display the videos and subjective questionnaires privately to each participant. A standard intercom was used for communication between the participant and female investigator, who was in the adjoining room.

Physiological Measures

As with our previous study, a region of interest on the left labia majora for women and the shaft of the penis for men were used for all analyses. A non-genital control on the upper right thigh served to determine the specificity of temperature change during sexual arousal.

Discrete Subjective Measures

Discrete, Likert-style questions concerning subjective arousal were asked at the outset of the experiment and then following each film via the

DVD goggles. Each question was pre-recorded and presented over the headphones with a corresponding scale shown on the screen for participants (see Appendix for list of questions).

Continuous Subjective Measure

In order to continuously record subjective sexual arousal, a

Windows-based computer program was developed similar to that of Rellini et al. (2005). This program required participants to use a standard PC mouse to indicate subjective ratings of sexual arousal. Participants noted changes in sexual arousal by clicking on the right mouse button for increases and the left mouse button when they felt decreases in their subjective sexual arousal. Our rating scale was from 0 to 10, with 0 equaling no sexual arousal whatsoever and 10 denoting the most sexually aroused that participants could feel in the laboratory context. The numeric level of arousal was indicated using auditory stimuli presented through a speaker located next to the examination table; each click on the mouse

was followed by an announcement of the number that participants had

indicated. The computer program recorded the level of subjective arousal

every second and an auditory reminder occurred if there was inactivity (no

clicking) for a 60 second interval. The familiarity that most participants

have with a computer mouse made this device relatively easy to use. Like

Rellini et al., we believe that using non-visual stimuli was less likely to

distract participants from the videos than previous continuous measures

that relied on participants viewing both their continuous scales and their

visual sexual stimuli. In addition, our program’s ability to remind

participants of their level of arousal after 60 seconds of inactivity

encouraged participants to continue using the measure throughout testing.

Procedure

The experiment was reviewed and approved by the McGill University

Faculty of Medicine Institutional Review Board; we obtained written informed consent from each participant.

Potential participants contacted the lab via telephone at which point study procedures were explained in detail and a telephone screening was conducted. Eligible participants were then scheduled for testing at our laboratory. When they arrived, the experimenter showed them the testing room as well as the adjoining data collection room. The thermal imaging equipment was demonstrated to them and participants were told that the experimenter would be monitoring their temperature and thermal image throughout testing. Participants were fully informed concerning the 97

purpose of the study and the procedures; however, they were not

informed about which experimental condition they were assigned to.

After informed consent was obtained, a brief semi-structured

interview was conducted to collect sociodemographic and basic health

and sexual health information (for list of questions, see Kukkonen et al.,

2007). Once the demographic variables were collected, participants were

left alone in the testing room for the duration of the experiment. All

communication was conducted over an intercom system with the female

research assistant in the adjoining room. Participants were instructed to

get undressed from the waist down, and men were asked to sit on the

examining table with their legs apart whereas women were asked to lie

back and place their legs in knee supports, similar to a gynecological

examination. All participants were instructed to put on the DVD goggles to

view the videos and questionnaires. The thermal imaging camera

recorded temperature for the duration of the experiment. Ambient room

temperature was monitored for each participant and was maintained so

that there was less than 1 °C variation within each testing session (M room temperature = 22.51, SD = 1.67).

The first 15-minute neutral video segment was used to allow for skin temperature to adjust and to stabilize (LaBarge, 2002). Following this

15-minute period, participants answered questions on subjective arousal, which were presented over the DVD goggles. Subsequent to the

questionnaire, all participants were shown another 15-minute neutral travelogue, which served as the baseline measure of their temperature

(Glusic, 1994). Subjective ratings of arousal were obtained once more through the questionnaire upon completion of the video. The final video sequence presented was either the sexually arousing video, the humorous film, the anxiety film or another neutral travelogue followed again by questions on subjective arousal (Blatt & Singer, 1983; Day et al., 2001;

Janssen et al., 2003; Vertue et al., 1999).

Throughout all three videos (stabilization, baseline, and experimental), participants continuously reported their subjective sexual arousal using the mouse. Once all three videos were viewed, participants were instructed to remove the goggles and to get dressed at their convenience. The investigator then met with each participant to discuss the study and answer any additional questions.

Data Analysis

Data analyses were conducted to examine the following hypotheses:

1. genital temperature increases would be specific to the

sexual arousal condition;

2. men and women would show no significant differences in

temperature change;

3. thigh temperature would remain stable throughout testing for

all conditions;

4. discrete and continuously measured subjective sexual

arousal would increase only during the sexual arousal film;

5. there would be a significant and positive relationship

between genital temperature and subjective sexual arousal

for both men and women.

In order to examine temperature differences between assigned film

conditions and genders, we averaged genital and thigh temperature

separately into three time intervals: 1) temperature during the first five

minutes (1-5 minutes); 2) mid five minutes (minutes 6-10); and 3) last five

minutes (minutes 11-15) of each film. A three-way ANOVA with one

repeated factor was then conducted on both genital and thigh temperature

for each period of recording (baseline and experimental). The independent

variables were sex, assigned film condition, and time of temperature

recording as the repeated factor. Similarly, to examine differences in the

continuous measure of subjective arousal by sexes and film condition, we

averaged participants’ continuous ratings into the same three time periods as their temperature and then conducted a three-way ANOVA with one

repeated factor to determine the significance of these differences at

baseline and during the experimental condition. To correct for violations in

sphericity, the Greenhouse-Geisser procedure was applied to the

100

repeated measures analyses; uncorrected degrees of freedom, but other corrected values are reported. Trend analyses were conducted following all significant interactions (p < .05) from the repeated measures ANOVAs.

Trend analysis takes into consideration the shape of the response curves and determines whether there were significant differences between groups in how the dependent variables (i.e., genital temperature and subjective sexual arousal) increased or decreased over time.

To assess duration of responding, analyses were conducted on the latency to maximal genital temperature and latency to maximal continuous subjective sexual arousal. These variables were assessed using univariate ANOVAs with assigned film condition and gender as the independent variables.

To examine baseline levels of subjective arousal, a multivariate

ANOVA was conducted on the discrete subjective arousal questionnaire.

As it was expected that there would be little variability in participant responses to each question during baseline, a principal components analysis could not be conducted for baseline levels of arousal. During the experimental condition, however, a principal components analysis with varimax rotation was conducted on the 13 arousal questions common to both sexes (excluding sex specific variables) to determine if a smaller number of stable factors could be used to assess subjective arousal.

Using Kaiser’s rule, only factors with eigenvalues over 1 were considered

101

significant. Furthermore, a factor was considered reliable only if it had three or more variable loadings above .8. Group differences in stable factors were then assessed using ANOVAs. All significant interactions (p <

.05) were followed by tests of simple main effects and Tukey HSD post- hoc analyses for ANOVAs. Finally, Pearson’s method was used to conduct correlational analyses on the relationship between discrete and continuous subjective sexual arousal, and the relationships between the physiological and the subjective measures of sexual arousal.

Results

Baseline Parameters1

In examining genital and thigh temperature across the baseline, analyses indicated that there were no significant differences between sexes or experimental conditions. Furthermore, there was no sex × assigned film condition interaction. Similar to the physiological data, there were no significant differences between sexes or assigned film conditions for both continuous and discrete measures of subjective sexual arousal during the baseline film.

Physiological Measures of Sexual Arousal

Average Genital Temperature

1 Results from the various F tests at baseline are available from the corresponding author upon request.

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To assess whether changes occurred in average genital temperature throughout testing, a three-way ANOVA with one repeated factor was conducted with sex and assigned film condition as the between subjects variables and time as the repeated measure. During the experimental condition, a significant interaction for sex × film condition ×

2 time, F (6, 142) = 4.16, p < .01, ηp = .15, and film condition × time, F (6,

2 142) = 15.01, p < .001, ηp = .39 (see figure 1) and was found.

In order to better understand the nature of the significant differences in average genital temperature over time, trend analyses were conducted via contrasts (p < .05). These contrasts revealed a significant difference in the linear trend for genital temperature in the erotic condition as compared to the three control conditions. An examination of Fig. 1 clearly displays a difference in the shape of the response curves with participants in the erotic condition showing a sharp linear increase in their average genital temperature over time while the three control conditions exhibited little or no change.

To further examine the significant interaction between sex and film condition over time, separate post-hoc contrasts were conducted within sexes and within film conditions (p < .05). When examining male participants only, there was a significant difference in the linear trend for average genital temperature that separated the erotic condition from all three control conditions. This difference was accounted for by the increase

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in genital temperature over time for the participants in the erotic condition and the relatively stable temperatures for those in the control conditions.

The same trend comparison for women revealed almost similar results: there was a significant difference in the linear trends for average genital temperature over time that separated the erotic condition from the humor and anxiety conditions, and a trend towards a significance between the erotic and neutral conditions (p = .057). Additionally, women in the anxiety condition had a decrease in genital temperature over time that created a significantly different linear trend from the three other film conditions. For both men and women, average genital temperature increased linearly throughout the erotic condition and remained stable or, in the case of the women in the anxiety condition, decreased, during the control films.

Contrasts within film conditions revealed no significant differences in average genital temperature over time between men and women within the neutral, humor or anxiety conditions. During the erotic condition, however, there was a significant linear trend that differentiated the men from the women. An examination of Fig. 2 shows clearly shows that this significant trend was accounted for by the greater intensity of average genital temperature responding over time for the men than women.

Latency to Maximal Temperature

Latency to maximal physiological arousal, or time to peak genital temperature, provides an indication of the duration of sexual responding.

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A two-way ANOVA was conducted on time to peak temperature with sex

and assigned film condition serving as independent variables. During the

experimental condition, there was a significant main effect for film

2 condition, F (3, 71) = 8.54, p < .001, ηp = .27.

A post-hoc analysis of time to peak temperature (p < .05) indicated

that participants in the erotic condition took significantly longer time to

reach peak temperature (M = 469.65 seconds, SD = 303.73) than those in

the humor (M = 150.05 seconds, SD = 188.85) or anxiety conditions (M =

149.37 seconds, SD = 199.96). There were no significant differences

between the erotic and neutral conditions (M = 413.00 seconds, SD =

298.39). In addition, participants in the neutral control condition took significantly longer to reach peak temperature than participants in the humor or anxiety conditions.

As there were no significant differences in the latency to maximal temperature for sex or sex × film, further analyses comparing men and women on this variable were not necessary.

Thigh Temperature

To determine whether temperature change during sexual arousal was specific to the genital region, thigh temperature was also recorded and analyzed. As with genital temperature, thigh temperature was averaged into three time periods. A three-way ANOVA on average thigh temperature, with sex and assigned film condition as the between-subjects

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variables and time as the repeated factor, did not reveal any significant

interactions.

Subjective Measures of Arousal

Average Continuous Measure of Subjective Sexual Arousal

Throughout each film, participant self-reported sexual arousal was continuously recorded and these data were analyzed using a 2 (sex) × 4

(film condition) × 3 (time) repeated measures ANOVA. There was a significant sex × film condition × time interaction, F(6, 142) = 2.87, p < .05,

2 ηp = .11, and a film condition × time interaction, F(6, 142) = 12.91, p <

2 .001, ηp = .35. Post-hoc contrast analyses (p < .05) revealed that the

erotic group showed significant differences in the linear and quadratic

trends of continuously reported subjective sexual arousal over time as

compared to the humor and anxiety conditions. In addition, participants in

the erotic condition showed significant linear trend differences from those

in the neutral condition. An examination of Fig. 3 clearly displays these

differences with participants in the erotic condition showing significant

increases in their continuous subjective sexual arousal over time while the

three control conditions exhibited little or no change. Tests of simple main

effects to determine the sex × film condition × time interaction revealed no

significant differences between men and women within each film

condition.

Latency to Maximal Reported Subjective Sexual Arousal

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To provide a comparison with latency to maximal physiological

arousal, an examination of time to peak continuous rating of subjective

sexual arousal was conducted. A two-way ANOVA with sex and assigned

film condition as the independent variables revealed a significant main

2 effect for film condition, F(3, 71) = 6.13, p < .001, ηp = .21. Post hoc

analyses (p < .05) show that participants in the erotic condition had a

significantly longer time to peak continuous sexual arousal rating (M =

431.90 seconds, SD = 320.25) than those in the humor (M = 131.15 seconds, SD= 257.22) or anxiety (M = 87.32 seconds, SD = 214.69) control conditions. There were no significant differences between the erotic and the neutral control condition (M = 304.70 seconds, SD

=335.74), and the three control conditions did not differ from each other.

Average Discrete Measures of Subjective Arousal

To assess discrete subjective arousal following the experimental condition, a principal components analysis with orthogonal varimax rotation was conducted on the 13 arousal questions common to both sexes (excluding sex specific variables) which resulted in two stable factors: Factor 1 accounted for 54.23% of the variance and consisted of all eight sexual arousal variables (eigenvalue of 7.21, rotated component loadings range from .76-.98); Factor 2 (eigenvalue of 2.55) accounted for

16.95% of the variance and consisted of three variables: anxiety (loading of .89), fear (loading of .82), and relaxation (loading of -.77). A third factor was identified and related to humor, but with only two significant loadings,

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it was not considered reliable. A 2 (sex) × 4 (film) ANOVA analysis conducted on each of the two reliable factors during the experimental condition revealed a significant main effect for film for the sexual arousal

2 factor, F(3, 71) = 103.54, p < .001, ηp = .81, and the anxiety factor,

2 F(3,71) = 30.30, p < .001, ηp = .56. Post hoc analyses (p < .05) revealed

that participants in the erotic condition scored significantly higher on

Factor 1 (sexual arousal) than those in the three control conditions. In

addition, the participants in the humor group had a significantly lower

score on this factor than those in the neutral condition. Regarding Factor 2

(anxiety), participants in the anxiety condition scored significantly higher

on this variable than those in the three other conditions. Finally, there was

one sex × film interaction for the sexual arousal factor, F(3, 71) = 5.72, p =

2 .001, ηp = .20, whereby women in the erotic condition had a significantly

higher mean score than men.

Influence of Camera on Subjective Sexual Arousal

When asked if the process of recording their genitals affected their

sexual arousal, 65% of the participants in the erotic condition responded

that it did not affect their arousal; 15% said that it increased and 20%

reported that it decreased their arousal (see Table 1). Participant reports

of intrusiveness or sexually enhancing effects of the thermographic

recording for each condition are shown in Table 1.

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Relationship Between Discrete and Continuous Subjective Sexual Arousal

Measures

To examine the relationship between the discrete subjective

arousal questions and the continuous measure, correlational analyses

were performed using Pearson’s method. Results indicated a significant

relationship between the sexual arousal factor from the principal

components analysis and each of the three continuous measure of

subjective sexual arousal averages (first 5 minutes, mid 5 minutes and last

5 minutes) with an r(77) of .78, .84, and .88 (p < .001) for the first 5 minutes, mid 5 minutes, and last 5 minutes, respectively. Using Fisher’s transformation, we determined that there were no significant differences between the correlations for men and women for any of the time periods

(1st 5 minutes: z = -.22; mid 5 minutes: z = 0; last 5 minutes z = .20).

Relationship Between Subjective and Physiological Measures

Latency to Maximal Self-Reported and Physiological Sexual Arousal

To examine whether there was a significant difference between time to peak continuous subjective ratings of sexual arousal and time to peak genital temperature, a paired samples t-test was conducted for participants in the erotic condition. This analysis revealed no significant difference in the time to peak continuous subjective sexual arousal and time to peak temperature during the erotic film.

Correlation Between Genital Temperature and Continuous Subjective

Sexual Arousal

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To examine the relationship between genital temperature and continuous subjective ratings of arousal, correlational analysis was performed using Pearson’s method on the average genital temperature for the first 5 minutes, middle 5 minutes, and last 5 minutes of recording and the average continuous rating for each of these time periods. Average genital temperature and average continuous subjective sexual arousal were significantly positively correlated for all three time periods (time period 1: r(77) = .26, p < .05; time period 2: r(77) = .41, p < .001; time period 3: r(77) = .46, p < .001). Furthermore, using Fisher’s transformation, we determined that there were no significant differences between the correlations for men and women during time period 2 (z =

.82) or time period 3 (z = .94). During the first time period, however, women’s genital temperature and average subjective rating was not significantly correlated whereas it was for the men, r(40) = .39, p < .05.

In addition to the between-subjects correlations, the continuous measure of subjective sexual arousal and continuous measure of genital temperature allow for within-subject correlations to be conducted for the participants in the erotic condition. By correlating the 900 temperatures

(one reading per second for 15 minutes) with the continuous measure ratings, the correlations were significant for all 10 men in the erotic condition, r(898) range .11 to .94, p < .05, and for 8 out of the 10 women, r(898) range .15 to .94, with three of those correlations being in the negative direction (see Table 2). The two women without significant

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correlations had no variability in their subjective sexual arousal—one reported a 10/10 for the duration of the video and the other remained at

0/10 throughout testing. To determine whether significant differences exist between genders for these within-subject correlations, an independent samples t-test was conducted on the average within subject correlation for men and the average within subject correlation for women. These results showed a trend towards significance, t(18) = 2.03, p = .06.

Correlation Between Genital Temperature and Discrete Subjective Sexual

Arousal Factor

To examine the relationship between genital temperature and subjective ratings of arousal, correlational analysis was performed using

Pearson’s method on the sexual arousal factor derived from the principal components analysis and the average genital temperature for the first 5 minutes, middle 5 minutes, and last 5 minutes of recording. Average genital temperature and the sexual arousal factor were significantly and positively correlated for the middle 5 minutes, r(77) = .38, p < .001, and last 5 minutes, r(77) = .46, p < .001, with a trend towards significance for the first 5 minutes, r(77) = .20, p = .07. Using Fisher’s transformation, we determined that there were no significant differences between sexes for these correlations (mid 5 minutes: z = .26; last 5 minutes: z = .75). When examining within men and women separately, the sexual arousal factor was not correlated with genital temperature during the first 5 minutes.

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Discussion

Results from this study indicated that thermal imaging could clearly detect and differentiate sexual arousal from neutral, humor, and anxiety control conditions in healthy 30-45 year old men and women. Participants in the sexually arousing condition experienced an average increase of

0.74°C in genital temperature from baseline to the erotic condition, as compared to decreases of 0.26°C, 0.44°C, and 0.57°C for participants in the neutral, humor, and anxiety conditions respectively. In addition, the

recorded temperature change was specific to the genitals as evidenced by

the stable temperature maintained in the thigh region throughout testing

for all participants. Finally, for both male and female participants, discrete

and continuous ratings of subjective sexual arousal increased during the

sexual arousal condition and demonstrated significant positive correlations

with genital temperature.

Overall, these data strongly support the validity of thermography as

a measure of physiological sexual arousal for both men and women.

Thermography provides an advantage to most previously used measures

in that it is not anatomy specific and can, therefore, be used for both

sexes. This limits instrumentation artifacts in comparing men and women

and enhances the applicability of the methodology. The use of both

positive and anxiety arousal control groups in our study also provided

strong discriminant validity for genital temperature as a measure of sexual

arousal and was in line with previous research using such control groups

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(Both et al., 2003; Kukkonen et al., 2007; Laan et al., 1995; Prause et al.,

2005). Furthermore, the data collected from a non-college age sample allowed us to generalize the methodology to a broader population and supported the results from our previous research (Kukkonen et al., 2007).

While there was likely self-selection bias in terms of the participants that volunteer for such research, this bias is problematic for all studies of sexuality (Janssen, 2001) and we have no reason to believe that our sample was any different from others doing similar research. The significant correlations with subjective measures of sexual arousal provided support for the convergent validity of genital temperature as a measure of sexual arousal. Finally, the inclusion of a measure of instrument intrusiveness provided valuable information on the perceived effect of the camera on sexual arousal and supported the ecological validity of the technique. Very few studies have examined the effects of instrument intrusiveness on sexual arousal. Prause et al. (2005) found a highly significant correlation between perceived discomfort of both the vaginal and labial photoplethysmographs and their level of interference in attending to films, which suggests that having an instrument that requires no contact would circumvent this distraction. It could be argued, however, that in the case of thermography, having a camera record genital temperature can differentially affect participants with varying levels of dispositional self-consciousness, something that was not measured in this study but should be examined in future research (Meston, 2006; van

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Lankveld, van den Hout, & Schouten, 2004).

Additional support for the ecological validity of this study was the relatively long presentation of continuous audiovisual sexual stimuli via videos. Recent research comparing subjective sexual arousal during different time intervals and different length video clips have demonstrated that subjective sexual arousal increased with length of film stimuli (Pfaus,

2008; Youn, 2006) and that genital response increased with stimulus intensity (Laan et al., 1995). The continuous 15 minute period of explicit audiovisual sexual stimuli used in this study may have allowed for higher levels of sexual arousal that are more akin to the natural pattern of sexual response than shorter time periods. Indeed, visual inspection of the raw temperature graphs demonstrated a leveling off of genital temperature following latency to peak in the erotic condition.

The results from this study were remarkably similar to those of our first thermography study with healthy 18-28 year olds (Kukkonen et al.,

2007). Men and women in both studies showed clear increases in temperature during sexual arousal that significantly correlated with their subjective report. Furthermore, there were no significant differences in the time it took men and women to reach peak temperature in either study, suggesting similarity in the pattern of sexual response between the sexes, which is also supported by early work from Rubinsky, Eckerman, Rubinsky and Hoover (1987). While these overall results replicated our first thermography study, interesting differences did exist. One such difference

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was the magnitude of temperature change. The 30-45 year old participants had an average increase of 0.74 °C during sexual arousal, whereas the 18-29 year olds had an average increase of 1.75 °C. This difference in the degree of temperature change supports previous research by Solnick and Birren (1977), who found significant decreases in the magnitude and rate of penile temperature change during sexual arousal between younger and older populations, and could indicate a change in physiological functioning with age, especially considering the similar levels of reported subjective sexual arousal between our age groups. There are numerous reports in the literature of changes in the mechanical and structural properties of human vasculature with aging, and this difference in the magnitude of temperature change during sexual arousal could reflect both the alterations within the endothelium with age whereby nitric oxide production decreases and endothelin production increases, as well as the changes in vessel properties, including vascular smooth muscle hypertrophy and reduction in capillary density that accompany aging (Holowatz, Thompson-Torgerson, & Kenney, 2007; Jani

& Rajkumar, 2006; Martin, Loomis, & Kenney, 1995; Schrage, Eisenach, &

Joyner,2007).

Men in the erotic condition showed a significant difference in the intensity of temperature change than the women. The sharper increase in temperature was possibly accounted for by the camera being focused close to the dorsal artery of the penis, which runs through the shaft, and

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likely increases temperature at a faster rate than the capillaries located

throughout the labia majora. Of note is that while men had an initial

sharper increase in temperature, women still reached peak temperature at

a similar time point, between minutes 7 and 9. This is suggestive of

similarities in the overall process of sexual responding. It is possible that

the similarities in time to peak temperature were an artifact of differing

visual stimuli; however, these results were in line with our previous study

whereby men and women both reached peak temperature between

minutes 11 and 13. Furthermore, research suggests that showing the

same video for men and women may not be ecologically valid (Janssen et

al., 2003). It is also possible that the lack of significant differences was

due to small sample size; however, a priori power calculations to

determine sample size suggest that this was likely not the case.

An examination of subjective sexual arousal revealed that both men

and women in the sexual arousal condition reported significantly greater

subjective sexual arousal than those in the neutral, humor, or anxiety

conditions. Of interest was that the women viewing the sexual arousal film

reported significantly greater sexual arousal than the men. Although this difference may be accounted for by differing video stimuli, it is also possible that the men were less comfortable reporting their subjective arousal to the female research assistant. Future research using the same video for men and women, in addition to have same-sex research

assistants, would help clarify the source of these differences.

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The relationship between women’s physiological and subjective sexual arousal has been controversial (Brotto & Gorzalka, 2002; Rellini et al., 2005; Laan & Janssen, 2007). Our study on younger participants, however, demonstrated a significant relationship for both men and women, though not during the first five minutes of testing for women

(Kukkonen et al., 2007). Similarly, this sample of 30-45 year olds revealed a significant relationship between genital temperature and the discrete report of subjective sexual arousal for the mid and last five minutes of testing but neither men nor the women showed concordance between these measures during the first five minutes. Additionally, the magnitude of the correlations appeared to differ between age groups with the younger participants having correlations of .50, .67, and .71 for the first five, mid five, and last five minutes of testing, whereas the older group had significant correlations of .38 and .46 for the mid five and last five minutes of testing only. This apparent difference in correlation may reflect the differences in temperature change, since the range of temperature increases during sexual arousal for the 30-45 year olds was less than that of the 18-28 year olds. It may also be that experiential generational differences, such as pornography usage, could account for these differences; however, this seems unlikely since rates of subjective sexual arousal were comparable between the different age groups.

When examining the relationship between the average continuous subjective sexual arousal and average genital temperature for the first

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five, mid five, and last five minutes of testing, there was a significant

relationship for the men at all three time points but only for the last two

time points for the women. It is possible that the initial increase in genital

temperature in women did not match their increase in subjective sexual

arousal; however, examining the change in average continuous sexual

arousal showed that the difference between baseline and the first five

minutes of the sexual arousal film was negligible. This discrepancy during

the first five minutes of the stimuli may very well represent a natural process whereby a participant’s motivation for sexual response was increased gradually through exposure to an explicit sexual stimulus and the first minutes of testing did not provide an adequate time frame for the

physiological and subjective responses to correspond. Another possibility

is that reducing the continuous subjective and physiological data to one

average time point during the first five minutes masked the initial changes

that are occurring. Rellini et al. (2005) have suggested that more sensitive

data analyses, such as hierarchical linear modeling, are required to

properly understand the relationship between physiological and subjective

arousal.

In conducting a within-subjects correlation for all 901 continuous

subjective arousal and temperature points, we found that all men in the

erotic condition demonstrated a significant inter-relationship; only eight out

of the ten female participants had such a relationship. The two women

without significant correlations showed no variability in their ratings of

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subjective sexual arousal with one reporting a 0/10 and the other reporting a 10/10 for the duration of the video. This lack of variability did not allow for correlations to be calculated. In addition, three women had significant negative correlations, which can be attributed to three genital temperature non-responders. For the women who did respond with increases in genital temperature during the sexual arousal film, the correlations were significant, with one having a low correlation (r = .15) and the other four having correlations above 0.80. These results were similar to previous research with continuous measures (e.g., Brody, 2007; Rellini et al.,

2005). Brody suggested that the variability can be accounted for by intercourse orgasm consistency. Unfortunately, we did not collect this data.

The existence of genital temperature non-responders is an interesting one and merits further investigation. It is certainly not uncommon in the literature to come across non-responders in sexual psychophysiology studies and there is an ongoing debate on what to do with their data (Janssen, 2006). In this sample, we had four female participants and one male participant who did not show increases in genital temperature during the sexually arousing film. Two of the women reported being highly sexually aroused subjectively throughout the presentation of all three video stimuli and thus may have already been at their maximal temperature from the outset, whereas the other two women reported increases in subjective sexual arousal but did not have

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corresponding changes in genital temperature during the sexual arousal

film. In contrast, the only male without increases in genital temperature

during the sexually arousing film also had no increases in his subjective

sexual arousal. Of interest is that there were no non-responders in our

initial study, which provides further support for the idea that there may be

an age-related change in vascular functioning accounting for the diminished physiological response during sexual arousal. It is possible that a lack of physiological response in the presence of subjective reports of sexual arousal could be a marker of future sexual arousal difficulties or even general vascular disorders. Indeed, there is a literature linking

decreased genital vascular response in men with a higher risk for more

generalized vascular disorders, such as coronary arterial disease

(Jackson, Rosen, Kloner, & Kostis, 2006; Vlachopoulos, Rokkas,

Ioakeimidis, & Stefanadis, 2007). Further examination of genital non-

responders is necessary to determine if there is any association with

decreased genital response, age, and future vascular difficulties.

Although this study clearly provided additional support for the use

of thermography in the physiological measurement of sexual arousal,

there were methodological limitations. At present, there is no standardized

method for examining the data, which means that the experimenter must

visually inspect that the region of interest remains fixed on the same

location throughout testing and manually move the region to correspond to

movement by the participant. While it is impossible to ensure that the

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precise location remains unchanged, it is unlikely that minor errors in adjustment would significantly change the results. Another limitation was that while temperature is easily comparable between individuals, it is not clear that a similar numeric change in temperature is directly equivalent in men and women or even in different age groups. It is also not clear how long genital temperature takes to return to baseline after the cessation of a sexual stimulus or how reliable it is between separate testing sessions

(Payne & Binik, 2006). A new study examining labial temperature using a thermistor, however, provided initial support for genital temperature returning to baseline within a ten minute period, making the use of within- subjects designs possible (Prause & Heiman, 2008).

Understanding all of these parameters better would allow for the use of thermography in within and between subjects group designs.

Future research on the concurrent validity of thermography, by comparing it to instruments that have been established as measures of sexual arousal, would also be useful. While previous research on penile temperature and penile plethysmography have shown high correlations, there are mixed results for the research on labial temperature and vaginal photoplethysmography (Fisher, Gross, & Zuch, 1965; Henson & Rubin,

1978; Henson, Rubin, & Henson, 1979; Prause & Heiman, 2008;

Rubinsky, Hoon, Eckerman & Amberson, 1985; Solnick & Birren, 1977;

Webster & Hammer, 1983). Finally, an examination of varying sexual film stimuli and detailed assessment of participant characteristics would

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provide insight into individual differences in genital temperature responding, in addition to further examining the similarities and differences between men and women.

We believe that thermography has great potential as a clinical diagnostic tool for the assessment and evaluation of sexual dysfunctions, such as erectile dysfunction, female sexual arousal disorder, and persistent genital arousal disorder. In addition, further examination of non- responders may provide useful information in determining markers of reduced vascular functioning. Finally, the ability to directly compare men and women makes this technology an ideal tool for the exploration of gender-specific theories of sexual arousal (Chivers, 2005).

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Appendix

Questions on subjective arousal (scale from 0-10 unless otherwise indicated):

Relaxation

1. Overall, how relaxed did you feel during this film?

Enjoyment

1. Overall, how much did you enjoy the film?

Humor

1. Overall, how funny did you find the film?

Anxiety

1. Overall, how anxious did you become during this film?

2. Overall, how frightening was this film?

Sexual Arousal

1. Overall, how sexually aroused did you become during this film?

2. How would you rate your peak sexual arousal?

3. Overall, how sexually aroused were you mentally during this film?

4. Did watching the video make you feel like having sex with a partner?

5. Did watching the video make you feel like masturbating?

6. Overall, how sexually aroused were you physically during this film?

7. How much genital change did you feel during this film?

8. Women only: how much lubrication did you feel during this film?

9. Women only: how much genital tingling or fullness did you feel during this film?

10. Men only: How would you rate your erection in response to this film?

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11. At what point during the film would you say that you were most sexually aroused (1)

was not at all sexually aroused; 2) within the first 5 minutes; 3) between 5-10 minutes; 4)

during the last 5 minutes; 5) varied throughout; 6) other)?

12. How sexually aroused did you feel during the film as compared to how sexually aroused

you typically are with a partner (–5 much less sexually aroused to +5 much more sexually

aroused)?

Influence of camera on arousal

1. Did the process of having your genitals filmed affect you in any way (Yes/No)?

2. If yes,

a) Did it increase or decrease sexual arousal?

b) To what extent (0 not at all-10 the most possible).

3. If yes,

a) Did it increase or decrease how funny you thought the film was?

b) To what extent (0 not at all-10 the most possible).

4. If yes,

c) Did it increase or decrease how relaxed you felt during the film?

d) To what extent (0 not at all-10 the most possible).

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Table 1. Percentage of Participants Who Indicated That Having a Camera

Film Their Genitals Increased, Decreased or Did Not Affect Their Sexual

Arousal.

Increase Decrease No Effect

Baseline 22.8% (N = 18) 8.8% (N = 7) 68.4% (N = 54)

Experimental

Neutral 10% (n = 2) 10% (n = 2) 80% (n = 16)

Humor 10% (n = 2) 5% (n = 1) 85% (n = 17)

Anxiety 10.5% (n = 2) 15.8% (n = 3) 73.7% (n = 14)

Erotic 15% (n = 3) 20% (n = 4) 65% (n = 13)

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Table 2. Within-Subjects Correlations for the Continuous Subjective

Sexual Arousal and Continuous Genital Temperature Recordings for Each

Participant in the Sexual Arousal Condition.

Male .11 a .46 a .51a .65a .70a .72 a .81 a .84 a .93 a .94 a

Female .00 .05 -.36a -.32a -.20a .15 a .84 a .85 a .89 a .95 a a p < .001

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34 Erotic Neutral 33.5 Humor Anxiety 33 A difference of this magnitude between groups is 32.5 significant at the .05 level

Temperature (degree Centigrade) (degree Temperature 32

31.5 First 5 minutes Mid 5 minutes Last 5 minutes Time

Figure 1. Average genital temperature for all the participants in the sexual

arousal (n = 20), neutral (n = 20), humor (n = 19) and anxiety (n = 20)

conditions, averaged across the first five minutes, mid five minutes and

last five minutes of the experimental condition.

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34 male

33.6

33.2 A difference of this magnitude between groups is 32.8 significant at the .05 level Temperature (degree Centigrade) (degree Temperature 32.4

32 First 5 minutes Mid 5 minutes Last 5 minutes Time

Figure 2. Average genital temperature for men (n =10) and women (n =

10) in the sexual arousal condition.

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8 Erotic 7 Neutral 6 Humor Anxiety 5 A difference of this magnitude 4 between groups is significant at the 3 .05 level 2

1 Subjective Sexual Arousal Rating Arousal Sexual Subjective

0 First 5 minutes Mid 5 minutes Last 5 minutes Time

Figure 3. Average continuous sexual arousal rating for all the participants in the sexual arousal (n = 20), neutral (n = 20), humor (n = 19) and anxiety

(n = 20) conditions, averaged across the first five minutes, mid five minutes and last five minutes of the experimental condition.

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UPDATE ON LITERATURE REVIEW

Since the publication of the three manuscripts in this dissertation, there have been several other studies conducted on the measurement of blood flow to the female genitalia. Seven publications have examined the use of ultrasonography, two have used laser Doppler imaging and two have examined labial temperature using thermistor clips.

With regards to ultrasound measurement, five studies have used this technology to examine and describe structural properties of the clitoris and pelvic region as well as to examine problems with genital vasculature in women (Buisson, Foldes & Paniel, 2008; Foldes & Buisson, 2009;

Gravina et al., 2008; Battaglia et al., 2009; Thorne & Stuckey, 2008). Two additional studies examined blood flow to the clitoris, one following treatment of vasomotor symptoms in postmenopausal women (Battaglia et al., 2009) and the other following treatment of sexual arousal disorder in women with type 1 diabetes (Caruso et al., 2006). Battaglia and colleagues (2009) found that the use of genistein, a phytoestrogen, decreased vasomotor symptoms in postmenopausal women, however, it did not significantly increase blood flow to the clitoris. Caruso and colleagues (2006), however, did find that treatment with Sildenafil significantly increased clitoral blood flow in women with type 1 diabetes who were exhibiting symptoms of sexual arousal disorder. Of note, is that none of these published studies measured clitoral blood flow during sexual

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arousal, rather, they all examined the hemodynamic properties of the clitoris either at rest or following the introduction of a vasodilating agent.

These studies show that ultrasound may be used to describe structural properties of the genitalia in women; however, our study suggests that this technology may not be ideal for the measurement of sexual arousal due to the lack of correlation with self-report and poor discriminant validity.

Another instrument that has been examined for the measurement of sexual arousal in women is laser Doppler imaging (Styles, MacLean &

Sultana, 2006; Waxman & Pukall, 2009). Styles and colleagues (2006) measured increases in blood flow to the vulva following exposure to read erotic passages, whereas Waxman and Pukall (2009) used the same video stimuli as we did to demonstrate significantly increased genital blood flow in healthy women during sexual arousal as compared to control conditions. Additionally, Waxman and Pukall found a significant relationship between genital blood flow and subjective sexual arousal.

Their research provides support for the measurement of labial blood flow as an indicator of physiological sexual arousal in women. An advantage of laser Doppler imaging is that it provides a direct measure of blood flow, which allows for the exact quantification of blood flowing through the genital region. This instrument, however, is very sensitive to movement artifact and as such, is impractical for use in men and by extension, the comparison of male and female sexual arousal. Additionally, laser

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Doppler imaging is not yet capable of continuous measurement, making it difficult to examine changes over time and fluctuations in arousal.

Finally, Prause and Heiman (2009; 2010) have renewed the examination of labial thermistors for recording sexual response in women.

Their research provides additional support for genital temperature as a measure of sexual arousal and demonstrates its sensitivity over vaginal photoplethymography (Prause & Heiman, 2009). In their recent study,

Prause and Heiman (2009) demonstrated that patterns of labial temperature change were significantly different during high and low intensity sexual arousal films whereas the output for vaginal photoplethysmography, vaginal pulse amplitude, did not differentiate between these conditions. In addition, Prause & Heiman (2010) found that women with lower reported sexual desire exhibited lower labial temperature than women with higher reported sexual desire, suggesting that genital temperature measurement has potential to differentiate sexually healthy women from those complaining of desire and arousal difficulties. One disadvantage of the labial thermistor, however, is the difficulty with proper placement. Prause and Heiman (2009) reported experimenters will likely have to manually place the instrument on participants as the participants themselves had great difficulty in properly securing the device.

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References

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E., & Venturoli, S. (2009). Genistein supplements might not induce

clitoral modifications in postmenopausal women: A prospective,

pilot study. Journal of Sexual Medicine, 6, 3132-3138.

Battaglia, C., Nappi, R. E., Mancini, F., Cianciosi, A., Persico, N., &

Busacchi, P.(2009). Ultrasonographic and Doppler findings of

subclinical clitoral microtraumatisms in mountain bikers and

horseback riders. Journal of Sexual Medicine, 6, 464-468.

Buisson, O., Foldes, P., & Paniel, B-J. (2008). Sonography of the clitoris.

Journal of Sexual Medicine, 5, 413-417.

Caruso, S., Rugolo, S., Agnello, C., Intelisano, G., Di Mari, L., & Cianci, A.

(2006). Sildenafil improves sexual functioning in premenopausal

women with type 1 diabetes who are affected by sexual arousal

disorder: A double-blind, crossover, placebo-controlled pilot study.

Fertility and Sterility, 85, 1496-1501.

Foldes, P., & Buisson, O. (2009). The clitoral complex: A dynamic

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Gravina, G. L., Brandetti, F., Martini, P., Carosa, E., Di Stasi, S., Morano,

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S., et al. (2008). Measurement of the thickness of the

urethrovaginal space in women with or without orgasm. Journal of

Sexual Medicine, 5, 610-618.

Prause, N. & Heiman, J. R. (2010). Reduced labial temperature in

response to sexual films with distracters among women with lower

sexual desire. Journal of Sexual Medicine, 7, 951-963.

Prause, N. & Heiman, J. R. (2009). Assessing female sexual arousal with

the labial thermistor: Response specificity and construct validity.

International Journal of Psychophysiology, 72, 115-122.

Styles, S. J., MacLean, A. B., Sultana, S. R. (2006). Laser Doppler

perfusion imaging: A method for measuring female sexual

response. British Journal of Obstetrics and Gynaecology, 113,

599-601.

Thorne, C. & Stuckey, B. (2008). Pelvic congestion syndrome presenting

as persistent genital arousal: a case report. Journal of Sexual

Medicine, 5, 504-508.

Waxman, S. E. & Pukall, C. F. (2009). Laser Doppler imaging of genital

blood flow: A direct measure of female sexual arousal. Journal of

Sexual Medicine, 6, 2278-2285.

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GENERAL CONCLUSIONS AND FUTURE DIRECTIONS

The three empirical investigations contained in this dissertation examine ultrasound and thermography as potential measurement technologies for sexual arousal in both men and women. Other existing technologies have all had significant practical and quantitative limitations that could be impeding the understanding of human sexual response.

Specifically, methodological artifacts could be contributing to the weak or non-existent correlations between physiological and subjective sexual arousal in women, the differences in sexual responding between men and women and the lack of physiological diagnostic criteria for women with arousal and desire disorders. The goal of our research was to evaluate different technologies that could be applied to both men and women for the measurement of sexual response and to address the existing limitations with measurement.

Ultrasound is commonly used to study penile vasculature and measure sexual response in men, and has been applied to the measurement of clitoral blood flow in women. An initial study by our research group demonstrated that two different ultrasonographers could reliably detect clitoral blood flow at rest (Khalifé, Binik, Cohen & Amsel,

2000), however, the results from the first empirical publication in this dissertation indicated that ultrasound measurement in women had poor discriminant and concurrent validity. While other research groups

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continue to use this instrument for describing anatomical structures in the pelvis, the research validating its use for the study of sexual arousal is minimal. Additionally, the high degree of variability found across women, and the intrusiveness of the procedure, significantly limit its potential as a widely used technology in sexual psychophysiology.

Contrary to the results from our ultrasound study, our initial work on thermography provided support for this measure as a basic tool to study sexual response in men and women. The use of thermography addressed many of the methodological concerns of existing instruments. It provided a continuous temperature measure on an absolute scale which can be used for between group comparisons. Thermography can be used to directly compare men and women as no genital manipulation or contact is required. Finally, genital temperature measurement was significantly correlated with subjective reports of sexual arousal for both men and women.

While thermography has much potential as a tool to study sexual arousal, there are additional methodological concerns that need to be addressed before this instrument can be applied to clinical research. One of the limitations with existing instruments is that longitudinal designs with multiple testing sessions are not possible because they have relative scales and highly variable outputs. This makes it difficult to examine the physiological effects of treatment interventions, for example, in women

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with arousal difficulties, and also makes it difficult to examine physiological

changes that may happen in sexual responding across the lifespan.

Furthermore, genital temperature measurement was originally criticized as

having a slow return to baseline (Payne & Binik, 2006), which has

impeded its use for studies that require multiple stimuli over a short period

of time. Prause and Heiman (2009) have recently demonstrated that the

latency to baseline is similar for labial temperature as it is for vaginal

photoplethysmography; we are also examining this issue in a recently

completed study using thermography.

In addition to examining latency to baseline, the above-mentioned

study was also designed to address the test-retest reliability of genital temperature measurement by having 40 healthy participants (20 men and

20 women) retested on three separate occasions. Initial analyses suggest that there are no significant differences in baseline genital temperature over the three sessions, nor are there any significant differences in genital

temperature during sexual arousal over the three sessions (Kukkonen,

Binik, Amsel & Carrier, 2010).

Finally, this study addressed a limitation from the two studies

included in this dissertation by examining the effect of showing the same

erotic videos to both men and women (as our initial studies use different

stimuli for each sex). We found no significant sex differences in the

correlation between genital temperature and self-reported sexual arousal

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for two of the three films used (Kukkonen et al., 2010). For the third film, both men and women exhibited significant relationships between physiological and subjective measures, however, the men had a significantly stronger relationship (pearson’s r = 0.76, p < .05) than women

(pearson’s r = 0.5, p < .05).

With the study of these methodological considerations completed, an interesting future direction is the examination of aging, genital vasculature and sexual response. In our first two studies, we showed significant differences in the degree of genital temperature change in a relatively young, healthy sample of men and women. We found that participants in the 18-28 year old age range had significantly greater temperature change than men and women in the 30-45 year old age range, despite similar reports of subjective sexual arousal (Kukkonen,

Binik, Amsel & Carrier, 2009). While age-related changes in genital vasculature are well-reported in men (Feldman et al., 1994), parallel physiological data in women is lacking. To further address this issue, we are completing a study expanding our findings to a sample of postmenopausal women and age-matched men. This data will allow us to examine cross-sectional changes in sexual responding with age and will provide initial normative data on genital response across the lifespan. If indeed there are physiological age differences in women as there are in men, then this research will help us determine how best to address clinical issues with sexual arousal across different age groups. 146

Another avenue of research that we are currently investigating is

the use of thermography to diagnose impaired sexual arousal. Our first

step in this direction is an ongoing study comparing thermography to

penile Doppler ultrasound for the diagnosis of erectile dysfunction in men.

For this study, participants complaining of erectile dysfunction undergo two assessment sessions, the first with thermography where genital temperature is measured during an erotic film, and the second with penile ultrasound, where a standard ultrasound assessment for erectile dysfunction is conducted. At present, we have recruited and tested 50 participants and initial impressions suggest that the two measures have concordance. Results from this research will help determine the utility of thermography as a clinical tool for men.

Finally, future endeavors will also include applications of thermography to the study of female sexual dysfunctions and to a broader health issues. Specifically, one of my goals for my newly appointed faculty position at the University of Guelph will be to examine whether diminished genital response during sexual arousal could be a risk factor for cardiovascular disease in women. In the final study of this dissertation, it was determined that there were a few women who showed no genital temperature changes during the sexual stimulus despite increased self- reported sexual arousal. It is possible that these women could be exhibiting early signs of vascular disease, much like what has been found in men with erectile dysfunction (Jackson, Rosen, Kloner & Kostis, 2006). 147

Indeed, self-reported dissatisfaction with sexual activity has been found in

women with peripheral artery disease (McCall-Hosenfeld et al., 2008),

however, there have been no studies measuring physiological sexual

response and cardiovascular diseases in women.

Additionally, I would like to examine the application of

thermography to women with sexual dysfunction. At present, there are no

physiological diagnostic criteria for women with sexual arousal disorders,

which makes diagnosis and treatment evaluation difficult (Rosen, Weigel

& Gendrano, 2007). With initial data collection being completed on

normative sexual response across the adult lifespan, I will begin to look at

women who complain of arousal difficulties to determine whether there

physiological differences in genital blood flow between sexually healthy

women and those complaining of arousal difficulties.

In addition to the work that our research group will continue to conduct using thermography, other laboratories across North America are also adopting this technology to examine sexual dysfunctions in men and women, vulvodynia and vaginismus in women and theories of sex differences. It is our hope that the research laid out in this dissertation has

provided a foundation for thermography to become a basic tool to study

sexual arousal and the interaction between physiological and

psychological processes.

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Appendix

Reprints of publications

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