DOCSLIB.ORG

Configural and Perceptual Factors Influencing the Perception of Color Transparency

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Configural and Perceptual Factors Influencing the Perception of Color Transparency CONFIGURAL AND PERCEPTUAL FACTORS INFLUENCING THE PERCEPTION OF COLOR TRANSPARENCY THÈSE NO 3181 (2005) PRÉSENTÉE À LA FACULTÉ INFORMATIQUE ET COMMUNICATIONS Institut de systèmes de communication SECTION DES SYSTÈMES DE COMMUNICATION ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE POUR L'OBTENTION DU GRADE DE DOCTEUR ÈS SCIENCES PAR Peggy GERARDIN licence de sciences cognitives, Université Lumière, Lyon 2, France et de nationalité française acceptée sur proposition du jury: Prof. S. Süsstrunk, directrice de thèse Prof. M. D'Zmura, rapporteur Prof. M. Herzog, rapporteur Dr K. Knoblauch, rapporteur Lausanne, EPFL 2005 Peggy GERARDIN THÈSE NO 3181 (2005) Acknowledgments Many people supported me during the completion of this thesis with criticism, helpful assistance and refer- ences. This work would have never been possible without them. First of all, I would like to express my gratitude to my supervisor Prof. Sabine Süsstrunk who gave me the opportunity to join her group, the best research environment I ever had. I would like to thank her for her guidance, encouragement and excellent advice throughout this study. I owe a special thank to Dr. Kenneth Knoblauch (INSERM U371, Lyon, France), whose patience, assistance and motivation were greatly appreciated. I stopped counting the numerous emails we sent to each other, the abundant lunches we shared and the million discussions we had on color vision. I would like to give a special thank to Prof. Michael D’Zmura, who welcomed me in his laboratory at the University of California, Irvine (USA). He proposed me a very interesting subject and helped me during all my stay. I thank him for the nice barbecues we had together and private concerts at home. I also thank Prof. Don Hoffman (UCI, USA) for the nice classes I attended to, and for the interesting discussions we had facing some good sushi. I thank all members of my thesis committee, including Prof. Michael Herzog, for accepting to read the thesis and to comment my defense. In particular, I would like to thank my colleague Roberto for being a very quiet officemate, not disturbing me with phone calls and not singing all day long, especially when I had to concentrate at work. I also thank Philippe for continuing working with me, even after his diploma. Many thanks to Vladan for the numerous coffee breaks, and to Jocelyne, Laurence, Patrick, Luciano, Andrea, Williams, Martin and all LCAV members, and for their interesting questions after each of my talks, such as ‘Do Inuits see colors like Europeans’? I really enjoyed working in this group. All my gratitude to my friends who shared these four years in Lausanne with me, in particular to David, Véronique, Elena, Gianluca, Gloria, Daniela and Stefan. I enjoyed travelling and partying with them, especially when I was discouraged and wanted to give up and become a florist. Also many thanks to Erin, for her gentleness and for the numerous rides we had in California. I also thank all my friends in France for their precious support. Last but certainly not least, I would like to thank my parents and my brother for their support and their numerous encouragements for each step that a thesis involves. I really enjoyed our relaxing and refreshing barbecues in our country house. Their visit in California was also one of my best memories. Finally, my warmest thanks go to Nicolas, for his understanding and his fantastic support. We endured numerous geographical distances during all my studies. During my thesis, a total of 72,240 km has been done to see each other. This does not include the time when I was in California. I dedicate this thesis to him, with love. iii iv Acknowledgments Abstract The mechanisms by which the brain represents colors are largely unknown. In addition, the large number of color phenomena in the natural world has made understanding color rather difficult. Color transparency perception, which is studied in this thesis, is precisely one of these interesting phenomena: when a surface is seen both in plain view and through a transparent overlay, the visual system still identifies it as a single surface. Processes of the visual system have widely inspired researchers in many domains such as neuro- sciences, psychology, as well as computer vision. The progress of digital imaging technologies requires research engineers to deal with issues that demand knowledge of human visual processing. To humans, an image is not a random collection of pixels, but a meaningful arrangement of regions and objects. One thus can be inspired by the human visual system to investigate color representation and its applicability to digital image processing. Finding a model of perception is still a challenging matter for researchers among multidisciplinary fields. This thesis discusses the problem of defining an accurate model of transparency perception. Despite the large number of studies on this topic, the underlying mechanisms are still not well understood. Investigating perceptual transparency is challenging due to its interactions with different visual phenomena, but the most intensively studied conditions for perceptual transparency are those involving achromatic luminance and chromatic constraints. Although these models differ in many aspects, a broad distinction can be drawn be- tween models of additive and subtractive transparency. The General Convergence Model (GCM) combines both additive and subtractive color mixtures in showing that systematic chromatic changes in a linear color space, such as translation and convergence (or a combination of both), lead to perceptual transparency. However, while this model seems to be a necessary condition, it is not a sufficient one for transparency perception. A first motivation of this thesis was to evaluate and define situations more general than the GCM. Several chromatic changes consistent or not with the GCM were generated. Additional parameters, such as configural complexity, luminance level, magnitude of the chromatic change and shift direction were tested. The main results showed that observers’ responses are influenced by each of the above cited parameters. Convergences appear significantly more transparent when motion is added for bipartite configurations, or when they are generated in a checkerboard configuration. Translations are influenced by both configuration and motion. Shears are described as opaque, except when short vector lengths are combined with motion: the overlay tends to be transparent. Divergences are strongly affected by motion and vector lengths, and rotations by a combination of checkerboard configuration with luminance level and vector length. These results question the generality of the GCM. We also investigated the effects of shadows on the perception of a transparent filter. An attempt to extend these models to handle transparency perception in complex scenes involving surfaces varying in shape and depth, change in conditions of illumination and shadow, is described. A lightness-matching task was performed to evaluate how much constancy is shown by the subject among six experimental conditions, in which shadow position, shadow blur, shadow and filter blending values were varied. The results showed that lightness constancy is very high even if surfaces were seen under both filter and shadow. A systematic deviation from perfect constancy in a manner consistent with a perceived additive shift was also observed. Because the GCM includes additive mixture and is related to color and lightness constancy, these results are promising and may be explained ultimately by this model. v vi Abstract Version Abrégée Les mécanismes par lesquels le cerveau se représente la couleur sont encore méconnus. De plus, le grand nombre de phénomènes colorés traités rend la tâche encore plus difficile. La perception de la transparence colorée, qui est étudiée dans cette thèse, est justement l’un de ces phénomènes : lorsqu’une surface est vue à la fois sous un filtre et en dehors, le système visuel l’identifie comme une seule et même surface. Les processus de traitement du système visuel ont largement inspiré les chercheurs dans des domaines aussi variés que les neurosciences, la psychologie et les sciences de l’informatique. Les progrès grandissants des technologies de l’imagerie numérique incitent les chercheurs à acquérir des connaissances sur le traitement visuel humain. Pour lui, une image n’est pas une collection de pixels, mais un arrangement de régions et d’objets qui a un sens. Il serait donc utile d’en être inspiré pour explorer la représentation de la couleur et ses applications dans le traitement de l’image numérique. Cette thèse traite du problème de définition d’un modèle précis de la perception de la transparence. Malgré le grand nombre d’études sur ce sujet, les mécanismes sous-jacents à ce phénomène sont encore peu compris. Explorer la perception de la transparence est un défi , dû à ses interactions avec de nombreux phénomènes visuels. Cependant, les modèles les plus étudiés sont ceux relatifs à la luminance achroma- tique et aux contraintes chromatiques. Même si ces modèles diffèrent par de nombreux aspects, ils peuvent être divisés en deux: les modèles de transparence additifs et soustractifs. Le Modèle Général de Con- vergence (GCM) combine ces deux mixtures de couleurs et montrent que des changements chromatiques systématiques dans un espace de couleurs linéaire, tels qu’une tranlation ou une convergence (ou bien la combinaison des deux), permettent la perception de la transparence colorée. Seulement, ce modèle est une condition nécessaire mais non suffisante à cet effet. Nous avons évalué et défini dans cette thèse des situations plus générales que celles qu’englobe le GCM. Plusieurs changements chromatiques cohérents et non cohérents avec ce modèle ont été générés. Des paramètres supplémentaires, tels que la complexité de la configuration, le niveau de luminance, la magni- tude des changements et leurs directions ont été testés. Nos résultats montrent que les réponses des sujets sont influencées par chacun de ces paramètres. Les convergences apparaissent plus transparentes lorsque le mouvement du filtre est ajouté pour les configurations de type bipartite, ou bien lorsqu’elles sont générées pour des configurations de type damier.
Load more

Recommended publications
  • Blindsight in Man and Monkey
    braini0301 Brain (1997), 120, 535–559 INVITED REVIEW Blindsight in man and monkey Petra Stoerig1 and Alan Cowey2 1Institute of Medical Psychology, Ludwig-Maximilians- Correspondence to: Petra Stoerig, Institute of Medical University, Munich, Germany and 2Department of Psychology, Ludwig-Maximilians-University, Goethestraβe Experimental Psychology, Oxford University, Oxford, UK 31, D-80336 Munich, Germany Summary In man and monkey, absolute cortical blindness is caused by degeneration. While extrastriate cortical areas participate in destruction of the optic radiations and/or the primary visual the mediation of the forced-choice responses, a concomitant cortex. It is characterized by an absence of any conscious striate cortical activation does not seem to be necessary for vision, but stimuli presented inside its borders may blindsight. Whether the loss of phenomenal vision is a nevertheless be processed. This unconscious vision includes necessary consequnce of striate cortical destruction and neuroendocrine, reflexive, indirect and forced-choice whether this structure is indispensable for conscious sight responses which are mediated by the visual subsystems are much debated questions which need to be tackled that escape the direct cerebral damage and the ensuing experimentally. Keywords: cortical blindness; blindsight; residual vision; phenomenal vision; visual system Abbreviations: dLGN 5 dorsal lateral geniculate nucleus; OKN 5 optokinetic nystagmus; PGN 5 pregeniculate nucleus; ROC 5 receiver-operating-characteristic curve Introduction ‘A survey of the recent literature indicates that the roˆle of gaining a better understanding of how the visual system the occipital lobes in visually guided behavior in general works and, by exclusion, of getting a hold on the neuronal cannot be properly evaluated as long as investigators are correlate of conscious vision.
    [Show full text]
  • Color Afterimages in Autistic Adults
    Color afterimages in autistic adults Article (Published Version) Maule, John, Stanworth, Kirstie, Pellicano, Elizabeth and Franklin, Anna (2018) Color afterimages in autistic adults. Journal of Autism and Developmental Disorders, 48 (4). pp. 1409-1421. ISSN 0162-3257 This version is available from Sussex Research Online: http://sro.sussex.ac.uk/id/eprint/61156/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher’s version. Please see the URL above for details on accessing the published version. Copyright and reuse: Sussex Research Online is a digital repository of the research output of the University. Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available. Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. http://sro.sussex.ac.uk J Autism Dev Disord DOI 10.1007/s10803-016-2786-5 S.I. : LOCAL VS. GLOBAL PROCESSING IN AUTISM SPECTRUM DISORDERS Color Afterimages in Autistic Adults 1 1 2 1 John Maule • Kirstie Stanworth • Elizabeth Pellicano • Anna Franklin Ó The Author(s) 2016.
    [Show full text]
  • Color Appearance Models Second Edition
    Color Appearance Models Second Edition Mark D. Fairchild Munsell Color Science Laboratory Rochester Institute of Technology, USA Color Appearance Models Wiley–IS&T Series in Imaging Science and Technology Series Editor: Michael A. Kriss Formerly of the Eastman Kodak Research Laboratories and the University of Rochester The Reproduction of Colour (6th Edition) R. W. G. Hunt Color Appearance Models (2nd Edition) Mark D. Fairchild Published in Association with the Society for Imaging Science and Technology Color Appearance Models Second Edition Mark D. Fairchild Munsell Color Science Laboratory Rochester Institute of Technology, USA Copyright © 2005 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (+44) 1243 779777 This book was previously publisher by Pearson Education, Inc Email (for orders and customer service enquiries): [email protected] Visit our Home Page on www.wileyeurope.com or www.wiley.com All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except under the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher. Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or emailed to [email protected], or faxed to (+44) 1243 770571. This publication is designed to offer Authors the opportunity to publish accurate and authoritative information in regard to the subject matter covered.
    [Show full text]
  • The Mccollough Effect: Dissociating Retinal from Spatial Coordinates
    Perception & Psychophysics 1993. 54 (4). 515-526 The McCollough effect: Dissociating retinal from spatial coordinates FELICE L. BEDFORD and KAREN S. REINKE University ofArizona, Tucson, Arizona Three experiments were conducted to dissociate the perceived orientation of a stimulus from its orientation on the retina while inducing the McCollough effect. In the first experiment, the typical contingency between color and retinal orientation was eliminated by having subjects tilt their head 90 0 for half of the induction trials while the stimuli remained the same. The only relation remaining was that between color and the perceived or spatial orientation, which led to only a small contingent aftereffect. In contrast, when the spatial contingency was eliminated in the second experiment, the aftereffect was as large as when both contingencies were present. Finally, a third experiment determined that part of the small spatial effect obtained in the first experiment could be traced to hidden higher order retinal contingencies. The study suggested that even under optimal conditions the McCollough effect is not concerned with real-world prop­ erties of objects or events. Implications for several classes of theories are discussed. The McCollough effect (ME) is viewed by some re­ how many pairs of attributes other than color and oriented searchers to be an instance of learning; the most well de­ lines can lead to contingent aftereffects (see Dodwell & veloped explanation in that class has appealed to Pavlov­ Humphrey, 1990; Harris, 1980; Siegel et al. 1992; ian conditioning (e.g., Allan & Siegel, 1986; Murch, 1976; Skowbo, 1984; Stromeyer, 1978)? Color can be made Siegel, Allan, & Eissenberg, 1992; Westbrook & Harri­ contingent on velocity, direction of motion can be made son, 1984).
    [Show full text]
  • –1– Study Guide for the Final Examination (Wednesday, 4 May
    Psychology of Perception Lewis O. Harvey, Jr.–Instructor Psychology 4165-100 Clare E. Sims–Assistant Spring 2011 09:30–9:45 TuTh Study Guide for the final examination (Wednesday, 4 May 2011, 16:30–19:00). Be able to answer the following questions and be familiar with the concepts involved in the answers. Review your homework and lab assignments and be familiar with the concepts included in them as well. 1. Draw a diagram of the eye including the following structures: cornea, lens, pupil, iris, sclera, aqueous humor, vitreous humor, choroid, retina, fovea, optic disk and optic nerve. 2. Offer an explanation of the Hermann Grid phenomenon based on ganglion cell receptive field characteristics. Why is this explanation insufficient? 3. What happens to contrast sensitivity and visual acuity as illumination goes down? Why is 3.2 Lux, the illumination level at the end of civil twilight, used as a rule-of- thumb reference level for the lower limit of practical visual performance? 4. Discuss the evidence that our color vision is based on three different types of cone receptors. 5. What are the major types of color defective vision and what are their causes? What kind of color experiences might a deuteranope have? Why 6. What is retinal disparity? How much disparity do you need for normal stereoscopic acuity? 7. Describe the “size/distance” (size constancy) hypothesis of certain visual illusions. Pick two such illusions and explain them in terms of this hypothesis. 8. A photograph is reproduced on a flat piece of paper. While you are viewing it, what could you do to enhance the impression of depth in a photograph? What are the basic principles? 9.
    [Show full text]
  • Fatigue and Structural Change: Two Consequences of Visual Pattern Adaptation
    Fatigue and Structural Change: Two Consequences of Visual Pattern Adaptation Jeremy M. Wolfe and Kathleen M. O'Connell In a tilt aftereffect (TAE) paradigm, 2 min of adaptation produced an aftereffect that decayed almost completely within 4 min. Four minutes of adapation produced a TAE that lasted more than 2 wk. Two modes of adaptation contribute to the TAE and account for other aftereffects: (1) short-term fatigue, produced very quickly and (2) long-term structural change, requiring more extended adaptation. Invest Ophthalmol Vis Sci 27:538-543, 1986 Two classes of visual aftereffects can be produced TAE can be measured at least 2 wk later. This extreme by adaptation to a visual stimulus: (1) The threshold persistence probably reflects structural change in the for detecting that stimulus and similar stimuli may be visual nervous system. raised,1 and (2) The suprathreshold appearance of re- lated stimuli may be altered (eg, orientation, motion, Materials and Methods 2 5 spatial frequency, and color). " Threshold elevation The basic TAE paradigm is shown in Figure 1. If aftereffects are explained as temporary reductions in the the reader fixates Figure la and then shifts gaze to lb, sensitivity of the mechanisms detecting the stimulus. it will be seen that lb comes to look like lc. These Adaptation fatigues the mechanism, and some period stimuli and the data presented below demonstrate that of time is required for recovery. Fatigue has been the TAE develops rapidly. With just these stimuli, proposed as an explanation of aftereffects of the second however, the reader will have more difficulty producing kind.5"7 However, several of these, notably the Mc- 5 8 the week-long TAEs that are the main topic of this Collough effect and the motion aftereffect can last paper.
    [Show full text]
  • Psychology of Perception Lewis O. Harvey, Jr.–Instructor Psychology 4165-100 Laramie E
    Psychology of Perception Lewis O. Harvey, Jr.–Instructor Psychology 4165-100 Laramie E. Duncan–Assistant Fall 2006 MUEN D156, 09:30–10:45 T&R Study Guide for the first examination (Tuesday, 17 October 2006). Be able to answer the following questions and be familiar with the concepts involved in the answers. 1. Describe the classical psychophysical methods of Fechner: the method of adjustment, the method of limits and method of constant stimuli. 2. Using your weight judgment experiment as an example, draw a psychometric function relating probability of making a “heavier” judgment to the weight of the test stimulus. Label both axes. Explain how the just noticeable difference (JND) is defined. Illustrate the JND on your graph of the psychometric function. 3. From the basic detection paradigm, define hit rate and false alarm rate. Describe the receiver operating characteristic (ROC) predicted by the High Threshold Model and the ROC predicted by the Signal Detection Theory of detection. How do you compute sensitivity (d’) from the hit rate and the false alarm rate for the equal-variance dual-Gaussian signal detection model? (Memorize the formula). 4. Be able to identify the following parts of the eye: cornea, lens, pupil, iris, sclera, aqueous humor, vitreous humor, choroid, retina, optic disk and optic nerve. 5. Define the term “receptive field.” Describe the receptive fields of retinal ganglion cells. How do ganglion cell receptive fields differ from those of cells in the primary visual cortex? 6. Describe and illustrate an explanation of the Hermann Grid phenomenon based on ganglion cell receptive field characteristics.
    [Show full text]
  • Visual Psychophysics and Sensitivity Regulation
    Visual psychophysics, sensitivity regulation and adaptation Moonlight Sunlight Typical ambient light levels Starlight Indoor lighting Photopic retinal illuminance -4.3 -2.4 -0.5 1.1 2.7 4.5 6.5 8.5 (log phot td) Scotopic retinal illuminance -3.9 -2.0 -0.1 1.5 3.1 4.9 6.9 8.9 (log scot td) Visual function Absolute rod Cone Rod saturation Damage threshold threshold begins possible NEUR 3045 Visual Neuroscience Andrew Stockman Psychophysical measures of adaptation mechanisms What is visual psychophysics? Psychophysicists study human vision by measuring an observer’s performance on carefully chosen perceptual tasks. By manipulating the properties of simple visual stimuli, and measuring the effect of that manipulation on an observer’s performance we can infer the way the visual system processes particular properties of a stimulus. INPUT PROCESSING OUTPUT How do we process visual ? information? STIMULUS VISUAL PERCEPTION SYSTEM What is visual psychophysics? In psychophysics, we try to infer what is going on inside the visual system just from studying the input and output. So, to the psychophysicist the visual system is much like a “BLACK BOX”. We can learn a surprising amount about the black box and how it works from psychophysical measurements. INPUT PROCESSING OUTPUT How do we process visual ? ? information? STIMULUS VISUAL PERCEPTION SYSTEM Psychophysical tasks that can provide useful information: DETECTION TASKS Is a circle present? Is the circle flickering Is the pattern (grating) or steady? visible? In general, simple tasks are used. Can you think of other tasks? Which other tasks provide useful information? DISCRIMINATION OR MATCHING REACTION TIME Are the two halves the same or different? Respond to the appearance of a circle as quickly as you can.
    [Show full text]
  • A Conditioning Model for the Mccollough Effect
    Portland State University PDXScholar Dissertations and Theses Dissertations and Theses 1975 A Conditioning Model for the McCollough Effect Andreas D. Lord Portland State University Follow this and additional works at: https://pdxscholar.library.pdx.edu/open_access_etds Part of the Psychology Commons Let us know how access to this document benefits ou.y Recommended Citation Lord, Andreas D., "A Conditioning Model for the McCollough Effect" (1975). Dissertations and Theses. Paper 2419. https://doi.org/10.15760/etd.2416 This Thesis is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. For more information, please contact [email protected]. AN ABSTRACT OF THE THESIS OF Andreas D. Lord for the Master of Science in Psychology presented July 31, 1975 Title: A Conditioning M~del ror ~he McCollough Effect APPROVED BY MEMBERS OF THE THESIS COMMITTEE: Gerald M. Murch, Chairman James Paulson A model based on the laws of classical conditioning is posed as an explanation for the McCollough Effect, an orientation-specific color aftereffect. This model stands as an alternative to the color-coded edge detector hypothesis. Background and relevant issues are presented, Two experi- ments were performed, The first demonstrated that an auditory stimulus causes the effect to appear stronger to some subjects, a disinhioiting effect, It was also shown that some subjects experience spontaneous recovery of the effect after it has bee~ extinguished, •\' is ; The second experiment demonstrated that the after­ colors will generalize to lines of varying orientation,. including ~5°. Subjects adapted to both red-vertical and green~horizontal lines ~aw mostly pink on test lines more than~30° off horizontal.
    [Show full text]
  • A Review of Visual Aftereffects in Schizophrenia T ⁎ Katharine N
    Neuroscience and Biobehavioral Reviews 101 (2019) 68–77 Contents lists available at ScienceDirect Neuroscience and Biobehavioral Reviews journal homepage: www.elsevier.com/locate/neubiorev Review article A review of visual aftereffects in schizophrenia T ⁎ Katharine N. Thakkara,b, , Steven M. Silversteinc, Jan W. Brascampa a Department of Psychology, Michigan State University, East Lansing, MI, United States b Division of Psychiatry and Behavioral Medicine, Michigan State University, East Lansing, MI, United States c Departments of Psychiatry and Ophthalmology, Rutgers University, Piscataway, NJ, United States ARTICLE INFO ABSTRACT Keywords: Psychosis—a cardinal symptom of schizophrenia—has been associated with a failure to appropriately create or Schizophrenia use stored regularities about past states of the world to guide the interpretation of incoming information, which Vision leads to abnormal perceptions and beliefs. The visual system provides a test bed for investigating the role of prior Aftereffect experience and prediction, as accumulated knowledge of the world informs our current perception. More spe- Adaptation cifically, the strength of visual aftereffects, illusory percepts that arise after prolonged viewing ofavisualsti- Predictive coding mulus, can serve as a valuable measure of the influence of prior experience on current visual processing. Inthis Excitation/inhibition balance Plasticity paper, we review findings from a largely older body of work on visual aftereffects in schizophrenia, attemptto reconcile discrepant findings, highlight the role of antipsychotic medication, consider mechanistic interpreta- tions for behavioral effects, and propose directions for future research. 1. Background system for understanding the role of experience in how individuals perceive and interpret the world and holds a clear translational value in Understanding the computational and neural mechanisms that understanding abnormalities in psychosis.
    [Show full text]
  • Visual Adaptation
    Swarthmore College Works Psychology Faculty Works Psychology 2000 Visual Adaptation Frank H. Durgin Swarthmore College, [email protected] Follow this and additional works at: https://works.swarthmore.edu/fac-psychology Part of the Psychology Commons Let us know how access to these works benefits ouy Recommended Citation Frank H. Durgin. (2000). "Visual Adaptation". Encyclopedia Of Psychology. Volume 8, 183-187. https://works.swarthmore.edu/fac-psychology/218 This work is brought to you for free by Swarthmore College Libraries' Works. It has been accepted for inclusion in Psychology Faculty Works by an authorized administrator of Works. For more information, please contact [email protected]. VISUAL ADAPTATION 183 Visual Memory points throughout the life span. Journal of the Optical Society of America A, 10, 1509-1516. Vision in complex environments requires observers not only to detect and discriminate stimuli presented si­ Robert Sekuler and Allison B. Sekuler multaneously, but also to integrate information appro­ priately over space and time. One index of this ability is short-term memory for visual attributes, such as spa­ tial frequency, that resist semantic encoding. Although VISUAL ADAPTATION refers to reversible changes in older observers typically perform poorly on tasks that perception caused by visual experience. For example, involve verbal memory, this age-related loss seems to after staring at the downward motion of a waterfall, a spare memory for visual attributes. Nevertheless, brain vivid sensation of upward motion will be perceived imaging (positron emission tomography) studies reveal when looking at a stationary object. Adaptation serves that different neural systems are responsible for spatial a functional role in the visual system by calibrating it frequency memory in younger and older observers (Mc­ to prevailing conditions and thus increasing the effi­ Intosh et al., 1997).
    [Show full text]
  • Introduction
    Andrew Stockman McCollough effect adapting pattern Colour Vision MSc Neuroscience course Andrew Stockman LONG-TERM “CONTINGENT” ADAPTATION Akiyoshi Kitaoka Light 400 - 700 nm is important for vision INTRODUCTION Lecture notes at http://www.cvrl.org Click on “MSc Neuroscience” in left menu. Colour Vision 1 Andrew Stockman No colour… How dependent are we on colour? Colour… But just how important is colour? Colour Vision 2 Andrew Stockman ACHROMATIC COMPONENTS CHROMATIC COMPONENTS Split the image into... CHROMATIC COMPONENTS By itself chromatic information provides relatively limited information… ACHROMATIC COMPONENTS How do we see colours? An image of the world is projected by the cornea and lens onto the rear surface of the eye: the retina. The back of the retina is carpeted by a layer of light-sensitive photoreceptors (rods and cones). Achromatic information important for fine detail … Colour Vision 3 Andrew Stockman Rods and Human photoreceptors cones Rods Cones . Achromatic . Daytime, achromatic night vision and chromatic vision . 1 type . 3 types Rod Long‐wavelength‐ sensitive (L) or “red” cone Middle‐wavelength‐ sensitive (M) or “green” cone Short‐wavelength‐ sensitive (S) or “blue” cone Webvision Rod and cone systems are optimized for different light levels Moonlight Sunlight Typical ambient light levels Starlight Indoor lighting Photopic retinal illuminance -4.3 -2.4 -0.5 1.1 2.7 4.5 6.5 8.5 (log phot td) Why do we have rods and cones? Scotopic retinal illuminance -3.9 -2.0 -0.1 1.5 3.1 4.9 6.9 8.9 (log scot td) SCOTOPIC MESOPIC PHOTOPIC Visual function Absolute rod Cone Rod saturation Damage threshold threshold begins possible Rod system Cone system A range of c.
    [Show full text]