DOCSLIB.ORG

Download Thesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Download Thesis This electronic thesis or dissertation has been downloaded from the King’s Research Portal at https://kclpure.kcl.ac.uk/portal/ Contextual Processing in Psychosis and Cannabis use Kane, Fergus Awarding institution: King's College London The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without proper acknowledgement. END USER LICENCE AGREEMENT Unless another licence is stated on the immediately following page this work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence. https://creativecommons.org/licenses/by-nc-nd/4.0/ You are free to copy, distribute and transmit the work Under the following conditions: Attribution: You must attribute the work in the manner specified by the author (but not in any way that suggests that they endorse you or your use of the work). Non Commercial: You may not use this work for commercial purposes. No Derivative Works - You may not alter, transform, or build upon this work. Any of these conditions can be waived if you receive permission from the author. Your fair dealings and other rights are in no way affected by the above. Take down policy If you believe that this document breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 05. Oct. 2021 This electronic theses or dissertation has been downloaded from the King’s Research Portal at https://kclpure.kcl.ac.uk/portal/ Title: Contextual Processing in Psychosis and Cannabis use Author: Kane, Fergus The copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without proper acknowledgement. END USER LICENSE AGREEMENT This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. http://creativecommons.org/licenses/by-nc-nd/3.0/ You are free to: Share: to copy, distribute and transmit the work Under the following conditions: Attribution: You must attribute the work in the manner specified by the author (but not in any way that suggests that they endorse you or your use of the work). Non Commercial: You may not use this work for commercial purposes. No Derivative Works - You may not alter, transform, or build upon this work. Any of these conditions can be waived if you receive permission from the author. Your fair dealings and other rights are in no way affected by the above. Take down policy If you believe that this document breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Volume I THESIS AND SERVICE PROJECT Dr Fergus Kane Thesis submitted in partial fulfilment of the degree of Doctorate in Clinical Psychology Institute of Psychiatry, King’s College London May 2012 Acknowledgements Many people have supported me during the process of completing this thesis, service project and case studies. However, before acknowledging all the wonderful people who have supported me, I must first apportion some blame; in particular to my brother, David, who one Christmas, showed me a paper by his PhD supervisor, Steven Dakin. The paper involved a fusion of two fascinating topics, psychosis and illusions. A brief discussion later, and we were wondering how this might fit with the effects of psychoactive drugs such as cannabis. Although I must accept some responsibility for what has happened since, David provided the triggering event. Some responsibility however, also lies with Paul Morrison and his team of cannabis researchers, who kindly let me bring my ideas to their study of the effects of cannabis compounds. Paul, Amir Englund, Judith Nottage, Dom Hague and Dominic ffytche were not only excellent collaborators, but also provided hours of stimulating conversation, some of which was about work. Similarly, I’d like to thank Oliver Suendermann, my good friend and collaborator on the second study of this Thesis. Without his help, this second study could simply not have happened. I’d like to acknowledge my two thesis supervisors, Suzanne Jolley and Dave Hemsley. Suzanne was everything one could wish for in a supervisor: kind, generous with her time, quick to respond, challenging and always helpful. Dave, although retired, kindly agreed to be my second supervisor and like Suzanne, could not have been a better choice. Dave’s knowledge of the literature, both past and present was a great help – he really did provide the context I needed to make sense of my work. More generally, thanks must go to my placement supervisors, Jerome Carson, Kitty Kwan, Sarah Addison, Catherine Jackman, Eric Morris, Nicola Reynolds and Laura Goldstein. To my Clinical Psychology coursemates, you’ve made this journey so much more in so many ways than it would have been without you. It’s been a real privilege to share my training with you. 2 To my family, once again, thank you for all your support and for providing a calm retreat for writing. This is the last thesis, I promise. Finally to Maria. Thank you for everything. I do not know a kinder and more generous person. 3 Contents of Volume I Main Thesis: Contextual Processing in Psychosis and Cannabis 6 use. Service Project. An Audit of Neuropsychological and 137 Psychometric Measures in South London and Maudsley National and Specialist Child Services 4 Main Thesis Contextual Processing in Psychosis and Cannabis use. Dr Fergus Kane Primary Supervisor: Dr Suzanne Jolley Secondary Supervisor: Professor David Hemsley 5 Abstract Introduction Cognitive models of psychosis highlight the role of underlying differences in cognitive function and information processing in the development and maintenance of psychotic symptoms. As a result there is now an interest in developing a greater understanding of these cognitive changes, in order to guide the development of evidence-based therapeutic interventions. An influential cognitive model of psychosis suggests that the core underlying cognitive difference in psychosis may be one of altered contextual processing. Recent work has suggested that this may be reflected in differential perception of visual illusions. However, it is not clear if such differences are present early in the development of psychosis. Such differences have also been reported to be associated with cannabis use. Further, it has been suggested that, in addition to being risk factors for the development of psychosis, psychoactive substances such as cannabis may provide a useful model for understanding psychosis. The current thesis thus investigated, in two separate studies: (1) the consequences of cannabis use on contextual visual processing and (2), whether reported contextual processing differences in psychosis are present at illness onset. Study One Two main hypotheses were tested. A. That THC, a key cannabis compound would reduce contextual visual suppression as measured using the Chubb illusion, and that this effect would be reduced via pre-treatment with another cannabis compound, cannabidiol (CBD). B. That THC would transiently induce symptoms of psychosis and that this increase would be reduced via CBD pre-treatment. No evidence was found to support the primary hypothesis. However, the secondary hypothesis was supported by the data. Study Two The primary hypothesis was that contextual visual suppression, again measured with the Chubb illusion, would be reduced in patients with first episode psychosis relative to a control group. Although not significant, the data supported this hypothesis. Discussion The results of Study One indicate that THC does not reduce visual contextual suppression as measured by the Chubb illusion. This is in contrast to evidence from other illusions, 6 and may reflect different neural mechanisms underlying contextual visual processing. However, the study provided clear evidence that THC can induce psychotic symptoms and that this effect can be reduced by CBD pre-treatment. Study Two replicates previous findings of reduced contextual processing in psychosis and provides evidence that this may be present from the onset of illness. These findings are discussed and interpreted with regards to study limitations, clinical implications and future work. 7 Table of Contents 1 INTRODUCTION 15 2 LITERATURE REVIEW 16 2.1 THE VALIDITY AND UTILITY OF THE TERM ‘SCHIZOPHRENIA’. 16 2.2 DIFFERENCES OF INFORMATION PROCESSING IN SCHIZOPHRENIA. 18 2.2.1 CONTEXT, SALIENCE AND DOPAMINE 19 2.3 COGNITIVE FUNCTION AND PSYCHOSIS: A BAYESIAN FRAMEWORK 22 2.3.1 THE BAYESIAN BRAIN: A VERY BRIEF PRIMER 22 2.3.2 THE BAYESIAN BRAIN: HOW IT MIGHT (NOT) WORK. 23 2.3.3 HALLUCINATIONS VS. PERCEPTUAL DISTORTIONS. A NOTE 25 2.3.4 VISUAL CONTEXT PROCESSING IN PSYCHOSIS. 26 2.3.5 SCHIZOPHRENIA SUBTYPES AND CONTEXT PROCESSING 32 2.4 CANNABIS AS A MODEL FOR UNDERSTANDING PSYCHOSIS 33 2.4.1 PHENOMENOLOGICAL SIMILARITIES BETWEEN DRUG INTOXICATION AND PSYCHOTIC DISORDERS. 34 2.4.2 CANNABIS AND THE CANNABINOID SYSTEM 36 2.4.2.1 Delta-9-tetrahydrocannabinol (Δ9-THC) 36 2.4.2.2 Cannabidiol (CBD) 37 2.4.2.3 A Potent Change 37 2.4.2.4 Subjective Effects of Cannabis 37 2.4.3 A BAYESIAN INTERPRETATION OF THE PSYCHOTOMIMETIC EFFECTS OF CANNABIS 39 2.4.3.1 Hallucinations. 41 2.4.3.2 Experimental Evidence of Cannabis Induced Reductions of Top-Down Processing 41 2.4.4 CANNABIS AND PSYCHOSIS: EVIDENCE OF A CAUSAL LINK. 42 3 AIMS AND HYPOTHESES 45 3.1 STUDY 1: THE EFFECTS OF THC AND CBD ON A TASK ENGAGING TOP-DOWN PROCESSING. 45 3.1.1 HYPOTHESES: 46 3.2 STUDY 2: AN INVESTIGATION OF CONTEXTUAL PROCESSING IN FIRST EPISODE PSYCHOSIS. 47 3.2.1 HYPOTHESES: 47 8 4 STUDY ONE. THE EFFECTS OF CANNABINOIDS ON CONTEXTUAL PROCESSING AND PSYCHOSIS SYMPTOMS 48 4.1 METHODS 48 4.1.1 ETHICAL APPROVAL AND CONSENT.
Load more

Recommended publications
  • Role of Stereopsis Losses in Older Adults’ Performance
    ROLE OF STEREOPSIS LOSSES IN OLDER ADULTS’ PERFORMANCE ON THE FINE-GRAIN MOVEMENT ILLUSION TASK by Marlena Pearson Honours Bachelor of Science, Psychology, Nipissing University, North Bay, Ontario, 2014 Honours Bachelor of Arts, Criminal Justice, Nipissing University, North Bay, Ontario, 2014 A thesis presented to Ryerson University in partial fulfillment of the requirement for the degree of Master of Arts in the program of Psychology Toronto, Ontario, Canada, 2017 © Marlena Pearson, 2017 Author’s Declaration AUTHOR'S DECLARATION FOR ELECTRONIC SUBMISSION OF A THESIS I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I authorize Ryerson University to lend this thesis to other institutions or individuals for the purpose of scholarly research I further authorize Ryerson University to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. I understand that my thesis may be made electronically available to the public. ii Role of Stereopsis Losses in Older Adults’ Performance on the Fine-Grain Movement Illusion Task Master of Arts, 2017 Marlena Pearson Psychology, Ryerson University Abstract Accurate motion perception is necessary for older adults to safely navigate their environments. Yet it is not clear how stereopsis losses contribute to findings of motion perception deficits in older adults. To assess the contribution of stereopsis losses, three groups (younger adults, older adults with intact stereopsis, older adults with poor stereopsis) were recruited for a fine-grain movement task.
    [Show full text]
  • Polarity Selectivity of Spatial Interactions in Perceived Contrast
    Journal of Vision (2012) 12(2):3, 1–10 http://www.journalofvision.org/content/12/2/3 1 Polarity selectivity of spatial interactions in perceived contrast Department of Psychology, The University of Tokyo, Japan,& Human and Information Science Laboratory, Hiromi Sato NTT Communication Science Laboratories, NTT, Japan Human and Information Science Laboratory, Isamu Motoyoshi NTT Communication Science Laboratories, NTT, Japan Department of Psychology, Takao Sato The University of Tokyo, Japan The apparent contrast of a texture is reduced when surrounded by another texture with high contrast. This contrast–contrast phenomenon has been thought to be a result of spatial interactions between visual channels that encode contrast energy. In the present study, we show that contrast–contrast is selective to luminance polarity by using texture patterns composed of sparse elongated blobs. The apparent contrast of a texture of bright (dark) elements was substantially reduced only when it was surrounded by a texture of elements with the same polarity. This polarity specificity was not evident for textures with high element densities, which were similar to those used in previous studies, probably because such stimuli should inevitably activate both on- and off-type sensors. We also found that polarity-selective suppression decreased as the difference in orientation between the center and surround elements increased but remained for orthogonally oriented elements. These results suggest that the contrast–contrast illusion largely depends on spatial interactions between visual channels that are selective to on–off polarity and only weakly selective to orientation. Keywords: polarity selectivity, spatial interactions, perceived contrast Citation: Sato, H., Motoyoshi, I., & Sato, T.
    [Show full text]
  • Visual Context Processing in Schizophrenia
    Empirical Article Clinical Psychological Science 1(1) 5 –15 Visual Context Processing in Schizophrenia © The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/2167702612464618 http://cpx.sagepub.com Eunice Yang1,2, Duje Tadin3,4, Davis M. Glasser3, Sang Wook Hong1,5, Randolph Blake1,2, and Sohee Park1 1Department of Psychology, Vanderbilt University; 2Department of Brain and Cognitive Sciences, Seoul National University, Republic of Korea; 3Center for Visual Science and Department of Brain and Cognitive Sciences, University of Rochester; 4Department of Ophthalmology, University of Rochester; and 5Department of Psychology, Florida Atlantic University Abstract Abnormal perceptual experiences are central to schizophrenia, but the nature of these anomalies remains undetermined. We investigated contextual processing abnormalities across a comprehensive set of visual tasks. For perception of luminance, size, contrast, orientation, and motion, we quantified the degree to which the surrounding visual context altered a center stimulus’s appearance. Healthy participants showed robust contextual effects across all tasks, as evidenced by pronounced misperceptions of center stimuli. Schizophrenia patients exhibited intact contextual modulations of luminance and size but showed weakened contextual modulations of contrast, performing more accurately than controls. Strong motion and orientation context effects correlated with worse symptoms and social functioning. Importantly, the overall strength of contextual
    [Show full text]
  • Optical Illusion - Wikipedia, the Free Encyclopedia
    Optical illusion - Wikipedia, the free encyclopedia Try Beta Log in / create account article discussion edit this page history [Hide] Wikipedia is there when you need it — now it needs you. $0.6M USD $7.5M USD Donate Now navigation Optical illusion Main page From Wikipedia, the free encyclopedia Contents Featured content This article is about visual perception. See Optical Illusion (album) for Current events information about the Time Requiem album. Random article An optical illusion (also called a visual illusion) is characterized by search visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are interaction different from the objects that make them, physiological ones that are the An optical illusion. The square A About Wikipedia effects on the eyes and brain of excessive stimulation of a specific type is exactly the same shade of grey Community portal (brightness, tilt, color, movement), and cognitive illusions where the eye as square B. See Same color Recent changes and brain make unconscious inferences. illusion Contact Wikipedia Donate to Wikipedia Contents [hide] Help 1 Physiological illusions toolbox 2 Cognitive illusions 3 Explanation of cognitive illusions What links here 3.1 Perceptual organization Related changes 3.2 Depth and motion perception Upload file Special pages 3.3 Color and brightness
    [Show full text]
  • Gaze-Contingent Visual Communication
    GAZE-CONTINGENT VISUAL COMMUNICATION A Dissertation by ANDREW TED DUCHOWSKI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 1997 Major Subject: Computer Science GAZE-CONTINGENT VISUAL COMMUNICATION A Dissertation by ANDREW TED DUCHOWSKI Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved as to style and content by: Bruce H. McCormick Udo W. Pooch (Chair of Committee) (Member) John J. Leggett Norman C. Griswold (Member) (Member) Wayne L. Shebilske Richard A. Volz (Member) (Head of Department) August 1997 Major Subject: Computer Science iii ABSTRACT Gaze-Contingent Visual Communication. (August 1997) Andrew Ted Duchowski, B.Sc., Simon Fraser University Chair of Advisory Committee: Dr. Bruce H. McCormick Virtual environments today lack realism. Real-time display of visually rich scenery is encumbered by the demand of rendering excessive amounts of information. This problem is especially severe in virtual reality. To minimize refresh latency, image quality is often sacrificed for speed. What’s missing is knowledge of the participant’s locus of visual attention, and an understanding of how an individual scans the visual field. Neurophysiological and psychophysical literature on the human visual system suggests the field of view is inspected minutatim through brief fixations over small regions of interest. Significant savings in scene pro- cessing can be realized if fine detail information is presented “just in time” in a gaze-contingent manner, delivering only as much information as required by the viewer. An attentive model of vision is proposed where Volumes Of Interest (VOIs) represent fixations through time.
    [Show full text]
  • Analysis of the Mechanisms of Human Visual Processing
    Christopher W . Tyler, Ph.D. Analysis of the Mechanisms of Human Visual Processing Christopher W. Tyler, Ph.D. Smith-Kettlewell Eye Research Institute 2318 Fillmore Street San Francisco, CA 94115, USA. Application for the degree of Doctor of Science University of Keele 1 Christopher W . Tyler, Ph.D. Education: Institution Degree Conferred Field of Study University of Leicester, U.K. B.A. 1966 Psychology University of Aston, U.K. M.Sc. 1967 Applied Psychology University of Keele, U.K. Ph.D. 1970 Communications Reseach and Professional Experience: 1990-2003 Associate Director, Smith-Kettlewell Eye Res. Institute, San Francisco, CA. 1981- Senior Scientist, Smith-Kettlewell Eye Res. Institute, San Francisco, CA. 1977- External Doctoral Thesis Advisor, Dept. of Psychology, University of California, Berkeley. 1986-87 Adjunct Professor, School of Optometry, University of California, Berkeley. 1985-89 Visiting Professor, UCLA Medical Center, Jules Stein Institute. 1978-80 External Doctoral Thesis Advisor, Dept. of Psychology, Stanford University, Stanford, CA. 1978-82 Honorary Res. Associate, Institute of Ophthalmology, London, U.K. 1975-81 Scientist, Smith-Kettlewell Eye Res. Institute, San Francisco, CA. 1974-75 Res. Fellow, Dept. of Sensory and Perceptual Processes, Bell Laboratories, Murray Hill, NJ. 1973-74 Res. Fellow, Dept. of Psychology, University of Bristol, U.K. 1972-73 Assistant Professor, Northeastern University, Boston, MA. (Psychology Courses: Experimental, Introductory, History, Social Issues, Vision). 1972 Visiting Assistant Professor, Dept. of Psychology, University of California, Los Angeles, CA. (Course: Perception). 1970-72 Res. Fellow, Dept. of Psychology, Northeastern University, Boston, MA. Dissertations M.Sc. A study of the electrical activity of the brain in a simple decision task.
    [Show full text]
  • Content-Prioritised Video Coding for British Sign Language Communication
    CONTENT-PRIORITISED VIDEO CODING FOR BRITISH SIGN LANGUAGE COMMUNICATION LAURA JOY MUIR A thesis submitted in partial fulfilment of the requirements of The Robert Gordon University for the degree of Doctor of Philosophy October 2007 Abstract Video communication of British Sign Language (BSL) is important for remote interpersonal communication and for the equal provision of services for deaf people. However, the use of video telephony and video conferencing applications for BSL communication is limited by inadequate video quality. BSL is a highly structured, linguistically complete, natural language system that expresses vocabulary and grammar visually and spatially using a complex combination of facial expressions (such as eyebrow movements, eye blinks and mouth/lip shapes), hand gestures, body movements and finger-spelling that change in space and time. Accurate natural BSL communication places specific demands on visual media applications which must compress video image data for efficient transmission. Current video compression schemes apply methods to reduce statistical redundancy and perceptual irrelevance in video image data based on a general model of Human Visual System (HVS) sensitivities. This thesis presents novel video image coding methods developed to achieve the conflicting requirements for high image quality and efficient coding. Novel methods of prioritising visually important video image content for optimised video coding are developed to exploit the HVS spatial and temporal response mechanisms of BSL users (determined by Eye Movement Tracking) and the characteristics of BSL video image content. The methods implement an accurate model of HVS foveation, applied in the spatial and temporal domains, at the pre-processing stage of a current standard-based system (H.264).
    [Show full text]
  • Free-Energy and Illusions: the Cornsweet Effect 058 002 059 003 060 004 Harriet Brown* and Karl J
    ORIGINAL RESEARCH ARTICLE published: xx February 2012 doi: 10.3389/fpsyg.2012.00043 001 Free-energy and illusions: the Cornsweet effect 058 002 059 003 060 004 Harriet Brown* and Karl J. Friston 061 005 The Wellcome Trust Centre for Neuroimaging, University College London Queen Square, London, UK 062 006 063 007 064 Edited by: 008 In this paper, we review the nature of illusions using the free-energy formulation of Bayesian 065 Lars Muckli, University of Glasgow, perception. We reiterate the notion that illusory percepts are, in fact, Bayes-optimal and 009 UK 066 010 represent the most likely explanation for ambiguous sensory input. This point is illustrated 067 Reviewed by: 011 Gerrit W. Maus, University of using perhaps the simplest of visual illusions; namely, the Cornsweet effect. By using 068 012 California at Berkeley, USA plausible prior beliefs about the spatial gradients of illuminance and reflectance in visual 069 013 Peter De Weerd, Maastricht scenes, we show that the Cornsweet effect emerges as a natural consequence of Bayes- 070 University, Netherlands 014 optimal perception. Furthermore, we were able to simulate the appearance of secondary 071 015 *Correspondence: illusory percepts (Mach bands) as a function of stimulus contrast. The contrast-dependent 072 Harriet Brown, Wellcome Trust Centre 016 073 for Neuroimaging, Institute of emergence of the Cornsweet effect and subsequent appearance of Mach bands were 017 Neurology Queen Square, London simulated using a simple but plausible generative model. Because our generative model 074 018 WC1N 3BG, UK. was inverted using a neurobiologically plausible scheme, we could use the inversion as a 075 019 e-mail: [email protected] simulation of neuronal processing and implicit inference.
    [Show full text]
  • Typical Lateral Interactions, but Increased Contrast Sensitivity, in Migraine-With-Aura
    vision Article Typical Lateral Interactions, but Increased Contrast Sensitivity, in Migraine-With-Aura Jordi M. Asher 1,* ID , Louise O’Hare 2 ID , Vincenzo Romei 1,3 and Paul B. Hibbard 1 1 Department of Psychology, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; [email protected] (V.R.); [email protected] (P.B.H.) 2 Faculty of Health and Social Sciences, Lincoln University, Brayford Way, Brayford Pool, Lincoln LN6 7TS, UK; [email protected] 3 Dipartimento di Psicologia and Centro studi e Ricerche in Neuroscienze Cognitive, Università di Bologna, Campus di Cesena, 47521 Cesena, Italy * Correspondence: [email protected] Received: 19 December 2017; Accepted: 7 February 2018; Published: 9 February 2018 Abstract: Individuals with migraine show differences in visual perception compared to control groups. It has been suggested that differences in lateral interactions between neurons might account for some of these differences. This study seeks to further establish the strength and spatial extent of excitatory and inhibitory interactions in migraine-with-aura using a classic lateral masking task. Observers indicated which of two intervals contained a centrally presented, vertical Gabor target of varying contrast. In separate blocks of trials, the target was presented alone or was flanked by two additional collinear, high contrast Gabors. Flanker distances varied between 1 and 12 wavelengths of the Gabor stimuli. Overall, contrast thresholds for the migraine group were lower than those in the control group. There was no difference in the degree of lateral interaction in the migraine group. These results are consistent with the previous work showing enhanced contrast sensitivity in migraine-with-aura for small, rapidly presented targets, and they suggest that impaired performance in global perceptual tasks in migraine may be attributed to difficulties in segmenting relevant from irrelevant features, rather than altered local mechanisms.
    [Show full text]
  • Do Illiterates Have Illusions? a Conceptual (Non)Replication of Luria (1976)
    J Cult Cogn Sci (2021) 5:143–158 https://doi.org/10.1007/s41809-021-00080-x (0123456789().,-volV)( 0123456789().,-volV) RESEARCH PAPER Do illiterates have illusions? A conceptual (non)replication of Luria (1976) Mrudula Arunkumar . Jeroen van Paridon . Markus Ostarek . Falk Huettig Received: 17 February 2021 / Revised: 17 February 2021 / Accepted: 21 May 2021 / Published online: 1 June 2021 Ó The Author(s) 2021 Abstract Luria (Luria, Cognitive development: Its Keywords Culture Á Literacy Á Visual perception Á cultural and social foundations, Harvard University Visual illusions Press, 1976) famously observed that people who never learnt to read and write do not perceive visual illusions. We conducted a conceptual replication of the Luria study of the effect of literacy on the Introduction processing of visual illusions. We designed two carefully controlled experiments with 161 participants Psychology, the study of human behavior, is not with varying literacy levels ranging from complete immune to the influences of Zeitgeist and the domi- illiterates to high literates in Chennai, India. Accuracy nant political movements and ideologies of the time. and reaction time in the identification of visual shape The history of psychology in the 1920s and 30 s and color illusions and the identification of appropriate includes dark chapters such as the eugenic movement, control images were measured. Separate statistical which aimed to provide (pseudo)scientific explana- analyses of Experiments 1 and 2 as well as pooled tions for the claim that desirable qualities are hered- analyses of both experiments do not provide any itary traits to justify white supremacy and scientific support for the notion that literacy affects the percep- racism.
    [Show full text]
  • Polarity Selectivity of Spatial Interactions in Perceived Contrast
    Journal of Vision (2012) 12(2):3, 1–10 http://www.journalofvision.org/content/12/2/3 1 Polarity selectivity of spatial interactions in perceived contrast Department of Psychology, The University of Tokyo, Japan,& Human and Information Science Laboratory, Hiromi Sato NTT Communication Science Laboratories, NTT, Japan Human and Information Science Laboratory, Isamu Motoyoshi NTT Communication Science Laboratories, NTT, Japan Department of Psychology, Takao Sato The University of Tokyo, Japan The apparent contrast of a texture is reduced when surrounded by another texture with high contrast. This contrast–contrast phenomenon has been thought to be a result of spatial interactions between visual channels that encode contrast energy. In the present study, we show that contrast–contrast is selective to luminance polarity by using texture patterns composed of sparse elongated blobs. The apparent contrast of a texture of bright (dark) elements was substantially reduced only when it was surrounded by a texture of elements with the same polarity. This polarity specificity was not evident for textures with high element densities, which were similar to those used in previous studies, probably because such stimuli should inevitably activate both on- and off-type sensors. We also found that polarity-selective suppression decreased as the difference in orientation between the center and surround elements increased but remained for orthogonally oriented elements. These results suggest that the contrast–contrast illusion largely depends on spatial interactions between visual channels that are selective to on–off polarity and only weakly selective to orientation. Keywords: polarity selectivity, spatial interactions, perceived contrast Citation: Sato, H., Motoyoshi, I., & Sato, T.
    [Show full text]
  • 1 Daily Vision Testing Can Expose the Prodromal Phase of Migraine
    Daily vision testing can expose the prodromal phase of migraine. Allison M. McKendrick1, Yu Man Chan1, Algis J Vingrys1, Andrew Turpin2, David R Badcock3 1 University of Melbourne, Department of Optometry and Vision Sciences, Melbourne, Australia 2 University of Melbourne, Department of Computing and Information System, Melbourne, Australia 3 University of Western Australia, School of Psychological Science, Perth, Australia Funding: Project supported by Australian National Health and Medical Research Council Project Grant APPID1081874 1 Abstract Background: Several visual tasks have been proposed as indirect assays of the balance between cortical inhibition and excitation in migraine. This study aimed to determine whether daily measurement of performance on such tasks can reveal perceptual changes in the build up to migraine events. Methods: Visual performance was measured daily at home in 16 non-headache controls and 18 individuals with migraine using a testing protocol on a portable tablet device. Observers performed two tasks: luminance increment detection in spatial luminance noise and centre surround contrast suppression. Results Luminance thresholds were reduced in migraine compared to control groups (p<0.05), but thresholds did not alter across the migraine cycle. While headache-free, centre-surround contrast suppression was stronger for the migraine group relative to controls (p<0.05). Surround suppression weakened at around 48 hours prior to a migraine attack and strengthened to approach their headache-free by 24 hours post-migraine (main effect of timing, p<0.05). Conclusions: Daily portable testing of vision enabled insight to perceptual performance in the lead up to migraine events, a time point that is typically difficult to capture experimentally.
    [Show full text]