DECEPTION IN FACIAL EXPRESSIONS OF PAIN: STRATEGIES TO IMPROVE DETECTION by MARILYN LOUISE HILL B.A. (Honours), Queen's University, 1989 M.Sc, Memorial University of Newfoundland, 1992 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Department of Psychology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA AUGUST 1996 © Marilyn Louise Hill, 1996 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) Abstract Research suggests that clinicians assign greater weight to nonverbal expression than to patients' self-report when judging the location and severity of their pain. However, it has also been found that pain patients are fairly successful at altering their facial expressions of pain, as their deceptive and genuine pain expressions show few differences in the frequency and intensity of pain-related facial actions. The general aim of the present research was to improve the detection of deceptive pain expressions using both an empirical and a clinical approach. The first study had an empirical focus to pain identification, and provided a more detailed description of genuine and deceptive pain expressions by using a more comprehensive range of facial coding procedures than previous research. A review of research on facial expressions, pain research and deception suggested that facial analyses of genuine and deceptive pain expressions could be expanded to include new variables such as temporal patterns and contiguity of facial actions, as well as an increased focus on facial cues thought to be indicative of lying. Low back patients (n=40) were videotaped at rest and while undergoing a painful straight leg raise under three sets of instructions: 1) to genuinely express any pain they felt, 2) pretend that it didn't hurt, 3) to fake pain without moving their legs. FACS coding was used to describe and quantify their facial activity and the neutral, genuine pain, masked pain and faked pain expressions were compared on the number, type, intensity, temporal qualities , and contiguity in time of individual facial actions, as well as the incidence of facial actions thought to be indicative of deception. Findings confirmed the difficulty of discriminating the various facial expressions, but indicated that the faked pain expressions show a greater number of pain-related and non pain-related actions, remain at peak intensity longer, and last for a longer period of time than do genuine pain ii expressions. The difference between masked pain and neutral expressions were more subtle, with masked pain expressions exhibiting a greater frequency of mouth opening and residual movement of the eyebrows. The second study was more clinical in nature and was designed to see if specific training could improve the detection skills of naive judges by increasing their knowledge and awareness of possible cues to deception. University students (60 male, 60 female) were randomly assigned to one of four experimental groups: l)control, 2) corrective feedback, 3) deception training, and 4) deception training plus feedback. Each subject was shown the videotaped data of the pain patients in all four conditions (neutral expressions, genuine, masked and faked pain expressions). For each videoclip, the subjects rated the intensity and unpleasantness of the pain experienced by the patient, decided which category each of the four videoclips represented, and described which cues they used to make their decision. There were significant individual differences in accuracy, with accuracy being unrelated to past pain experience, empathy, or the number or type of facial cues used. There was, however, a significant sex difference in judgement accuracy, with females being more accurate than males. Results also showed that immediate corrective feedback led to significant improvements in subjects' detection accuracy, while there was no support for the use of an information-based training program. iii Table of Contents Pag Abstract : ii Table of Contents iv List of tables ix Acknowledgement xi Introduction 1 Literature Review ; 4 Describing genuine and deceptive pain expressions 4 Facial expressions of pain 5 Factors contributing to the discrepancies in pain expression research 5 Type and severity of pain 5 Methodological differences 7 Situational variables 8 Validity and utility of the pain expression 8 Discriminating genuine versus deceptive pain expressions 11 Genuine pain..... 11 Faked pain 12 Masked pain 12 Individual difference variables 14 Summary J. 15 Deception theory and research '. 16 Types of deception 16 Theoretical basis for differences between genuine and deceptive expressions 17 Cues to deception 18 Concealing a genuine expression 18 Falsifying an expression 18 Temporal qualities of facial expressions 19 Temporal contiguity of pain expressions 19 Patterns of facial expression 20 iv Blinking 21 Asymmetry 22 Describing and quantifying facial expressions 25 Increasing the comprehensiveness of FACS coding 25 Detecting pain through facial expression 26 Judging genuine pain using facial expression 27 Detecting genuine versus deceptive pain 28 Detecting deception in others 30 Individual differences in detection accuracy 32 Possible individual difference variables 32 Cue utilization 32 Decision-making confidence 33 Sex differences 34 Empathy 35 Summary 36 Training to improve lie detection 36 Prospects for deception training specific to pain .....37 Summary 40 Study one: A comprehensive description of genuine and deceptive pain expressions ....41 Hypotheses 42 Study two: Effectiveness of training strategies to improve the discrimination of genuine and deceptive pain expressions 43 Hypotheses 43 Study one: Analysis of genuine, faked and masked pain expressions 44 Method 44 Subjects 44 Videotape equipment 44 Coding videotape 44 Measures 45 Personal data sheet 45 Descriptor differential scales 45 v Procedure 45 Videotaping protocol 46 Quantification of facial activity 47 Results 49 Description of patient population 49 Reliability coding 49 Preliminary analyses 50 Frequency 50 Intensity 54 Apex duration 57 Onset duration 58 Facial action duration 58 Asymmetry and pulsating apexes 63 Temporal contiguity of facial actions 63 Study two: training to detect deception 65 Method 65 Subjects 65 Materials 65 Video equipment 65 Videotape 65 Training manual 66 Measures 66 Personal information sheet 66 Interpersonal Reactivity Index 67 Procedure 67 Training conditions 67 Judgement task 68 Results 69 Judgements of pain 69 Sex 69 Training group 69 vi Pain condition 73 Perceived judgement accuracy 74 Decision-making process variables 74 Number of cues used 74 Type of cues used 77 Individual difference variables 85 Pain experience 85 Empathy 86 Comparison of successful and unsuccessful judges 87 Discussion 88 Describing genuine and deceptive pain expressions 88 Genuine pain expressions 88 Faked pain expressions 90 Masked pain expressions 92 Individual differences in facial expressions of pain 93 Temporal qualities of deceptive versus genuine pain expressions 94 Incidence of deception cues in deceptive vs genuine pain expressions 95 Summary 95 Detecting genuine and deceptive pain displays 96 Judgements of intensity and unpleasantness 97 Discrimination of genuine and deceptive pain expressions 99 The effects of training on facial expression judgements 101 Individual differences in judgement accuracy 104 Sex differences 105 Pain experience and empathy 106 Comparison of successful and unsuccessful judges 107 Summary 107 Future directions 108 Limits to generalizability 109 vii References Ill Appendices Appendix A: FACS action units 118 Appendix B: Research identifying pain-related AU's 119 Appendix C: Study one questionnaire package 121 Appendix D: Consent form for pain patients 124 Appendix E: Physiotherapy protocol 125 Appendix F: Descriptor differential scales 126 Appendix G: Training manual 128 Appendix H: Questionnaire package 142 Appendix I: Videotape description and rating forms 147 Appendix J: Frequency of facial cue use per subject 151 Appendix K: Categorization of facial cues 156 Appendix L: Type and frequency of subjects' pain experiences 158 Appendix M: Correlation matrix 159 viii List of Tables Table Page 1 Results of MANOVA and Followup ANOVA's Examining Frequency of Facial Actions Across Pain Conditions 51 2 Mean Facial Action Frequency Across Pain Conditions 52 3 Results of MANOVA and Followup ANOVA's Examining Intensity of Facial Actions Across Pain Conditions 55 4 Mean Facial Action Intensity Across Pain Condition 56 5 Results of MANOVA and Followup ANOVA's Examining Apex Duration of Facial Actions Across Pain Conditions 59 6 Mean Facial Action Apex Duration Across Pain Condition 60 7 Results of MANOVA and Followup ANOVA's Examining the Duration of Facial Actions Across Pain Conditions 61 8 Mean Facial Action Duration Across Pain Condition 62 9 Results of MANOVA on the Effects of Sex, Training and Pain Condition on Judgements