Early Experience and Visual Information Processing In

Total Page:16

File Type:pdf, Size:1020Kb

Early Experience and Visual Information Processing In DOCUMENT RESUMF In 113 681 ee tri ---... CS 002 179 . ./ AU"IOF Young, Francis A., 1; Lindsley, Depall_B.0 Ede TTI"LT - FerIy Experience and Visual Informaii,ion Processing in Perceptual and 'leadi641 PisordArs; PrOceedings ofa ConferencA Held October 27-3n, 1968, At Lake Mohonk, New York, in Association with.the,Committee on Brain Sciences, Div. of Medical ScienceP; National 'Research Council. TNSTTTUTTON National Academy of- Sciences -.National Pasearch Council, liashington, D.C. PUB IgTis 71't NOT? 538p 'AVAIL' tnr.FPOM Printing and Publishing Office, National Acadeiy of Sciences, 2101 Constitution Avenue, Washing4:on, D.C. 20116 ($9:951 3DRS PPTC",, FF-$ ^.92 Plus Posatage. HC Not Available frokEDRS. r n'SCTIPTnPS Anthologies; Cogni.4%ive Processes; Conference Reports; Early Feeding; Eye Movements; Information Theory; . *reading Difficulty; *Peading Processes; *Reading research; Remedial Reading; *Vision; *Visual Perception % - ABSTRACT . A , This book brings together papers presented ata conference on early experience and visual inforiaitien processing in perceptual and readin5 disorders sponsored by the kttional Academy` of Sciences. The goal of the conference was to integrateebtsic knowledge . of structure and mechanisms of eye and brain with their function and *heir behavioral roles in'perceptione'rdth the focuson underlying factors *hat may contribute to reading disorders. The first section discusses topics related to the role of the- visual system: optical and oculomotor, retinal, and central neural faretos.LThe second eectionxdiscusses attentional and perceptual itechanims. The thir section discusses early experience and learning' in visaal.information proce sing: The fourth section discusses the role of information pros isssing in perceptual and reading disabililties. The fifth and fin 1 section discusses management of childre with perceptual and reading disabilities. The introduction is written by DonaldLindsley and Francis Young. Individual papers are written by such authorsas Jeanne Chan, Pobert Boynton, Pobert Doty, roger Sperry, Richard Jung, George Sperling, Ira Hirsh, Merton Flom, Wi114am Mason, Robert Fantz, and H. Burtt Pichardson,.Jr. (TS) **** ****************************Ji*********************************** Documents acquired by ERI,C inclu4? many informal unpublished * materials not available from other soArces. EPIC makesevery effort * * to obtain the best col)! available. Nevertheless, items of marginal * * reproducibility aresoften encpunte,red Mid this affects the quality * * of ..he, microfiche and hardcopy reproductions EPIC makes%available * * via he !RTC Document Reproduction Service (BIM). EDRS is not '4, responsible for the quality of the original document., Reproductions * . * supplied by Errs are the best that cah be made from the .original. ** ****s****************************************************************** ut Oa PAII3;oaiif OR 1.04.144 DotAfPOPP a VollsJPAltt 1OFFC-JIC6011 I.._ . -1 o \ N , i' FRANCIS .4 YOUNG !DONALD B. LIDSLEY Early Experience and Visual F;111,,,to..10wl ruOtPviI14.'. ` OPPP.,,,, I ksPoliv.AL ay miCgio Infoimation Processing 1,4.NE ONLY *Pa,Pkt FP.<1.149D RV 44(444 V, t 1141AtilD Oui,ouviaTo..Tho, ONE, Ray P. V.001i tt AC.OttEMItp.r;4.114YmtNA in PeiPtuar and ErwCAP,OP. Iu...t.orp.(4111Pi100. '110% 0%01,IOr Pup I frPs: WEQuo,c1P PCPP.S Recling DisOrder$, 1.4 cesrPtsor.... ot,P.1-1 Proceedings of a Conference held October 27-30. 19,Y, at Lake ,i'Mohonk. kw York, in association with the Contmittee On Brain Sciences. Division of Medical Sciences, lit National 'Research Council C\if NATIONAL ACADEMY OF SCIENCES \VASA! ING1 ON, D.C. 1970' 02 The conference was supported by Public Health Semce contract Pf143*4744.1ask order 38. froin the National Institute of Neurological Diseases and-Stroke. Published by the aid of the Edmond and Marianne Bladsv Ophthalmology Fund ISBN 0-309-01765-3 Available front Printing and Publishing Office National Academy of Sciences 2101 Constitution Avenue Washington, D.C. 20418 First printing, October 1970 Second printing, September 1971 No, Library of Congress Catalog Card Number 72. 605763 03 I / .1 Foreword et A Lake Molionk Mountain House has a history of hosting altruistic meet- ings long before they became so popular. In 1883, the first conference of Friends of the Indians was held there, a conference that laterwas ,broallervidlo include a more general subject. ".4ke Mohank Conference of Friends of the Indian and Other Dependent Peoples." In 1895,a con- ference on international arbitration met there. The dismal-history of these subjects since then testifieS that more than motivation and intelli- Once are needed to transform successful conferences intoaMion. More than twenty years ago, it was obvious that, given sufficient funds, scientists and engineers could put courageous menon the moon because these efforts would not be hampered by superstitionlioblems of brain and behavior are another matter and in the opinion of any people constitute a most important frontier. Although there have been no comparable dramatic and highly visible breakthroughs in the knowl- edge of the mechanisms of childhood development, there has beena quiet revolution in the knowledge of how the child develops. It isnow rtcogniied that from birth to three years isan age of sinister importance. The hope is that similarly objective studies of hOw development pro- ceeds will be extended (and supplement existing observations of the pe....;od) to seven years of age, when the child enters public life in the school situation. V . 04 Fore ivfml It has Feen apvarent since MO that cognitive development is not depen,dent on motor ack.omplishments-. It might seeitito he only a small step 10.inu observation of overt actions in infants three to six month4 old to t.areful observations of visual attention to various objects!at a few . days of age, but the results have been revolutionary in directing atten- non to the -sdiemata of cognitive development at the earliest age. Instinc- tual behavior in human infants may be considered minimal, the sucking, reflex, the Li-) mg signal, and perhaps imitative reactions, early body play mg, and infantile sexuality belong in this category. The quiet revo- 1 lution of the last decade has taken infancy out bf the realm of concern/ about primary necessities of vegetation and into the sphere of the fully -P living human being and has shown that cognitive learning and socializf (ion can begin at a very early age. Parents who have the interest and, ability to understand its importance have accomplished thistransition urAuld-rearnig fairly well on a naturalistic, almost subconscious,/level. Those children whose parents are too harried by economic or other problems are not so fortunate. The t.Afererice speakers put the problem in bold relief. Although the research studies described einphasize the importanCe of exteroceptive stimulation of the infant, they by no means derogate the importance of somatusensory and motor functions' and loving maternal and paternal Bare. Tiro capacity of the very young infant to find intellectual pleasure in manipulating a mobile, for example, was documented, but theinfant -can and often does receive similar "education" from an old tin canif there is the emotional security of parental care and affection. The conferenCe was notable for its scientific objectivity. The goal was to bring people -of diverse disciplines together to communicate on the role of early experience in visual information processing. Discussions were confined to the subject With no "practical" implications for belief- system conditioning techniques. The general tune was free of acrimoni- ous arguments, as if each participant knew that the issues were too important to permit personal polemics. Even during the extracurricular hours, when individual differences of opinion were more openly ex- pressed, the arguments, although pointed, were urbane and friendly. There was a remarkable demonstration of the free-inquiry approach to complex problems. The data were the result of hardheaded and disci- plined naturalistic observations gently and skillfully guided by instru- .orented measurements and manipulation of the environment. Freud, Watson, Gesell, Piaget, and many other pioneers were present in the Pi 4 . backgrouq, obviously inspiring or provoking the investigators, but sreverdonunating-the Scene. I was impressed by the emphasis on the necess' ity of integration of two or inure sens-orimotor facilities. One wonders about the phenomenoii of Helen Kdler and is led to the speculation thata facility not properly used may have a negative effect on other facilities, This sugges,tiOn may' answer.some of the puzzles }!resented. Appropriate attention was paid to the handicapped child. but what stood out was the_needfor greater uuderstarkding of "normal"(Aiwa- normal developmental problems. studies of "normals" giiegreat insight into the problems of the marginal child. This volume of proceedingsis a valuable supplement to the three-year study of the Jbint.Commissiontan Child Mental Health, which represents onlyone of many, farge-scale at- tack on the problems of child developmentnow receiving wide public attention. and it lends perspectise to the work of the Interdisciplinary Committee on Reading Problems and the,National Adv isory Committee on Dyslexia and Related Reading Disabilities. Myse was brought out at the conference than is immediately apparent. If the child from birth to three y ears of agecan gain such emotional and intellectual satisfaction from
Recommended publications
  • Geometry of Some Functional Architectures of Vision
    Singular Landscapes: in honor of Bernard Teissier 22-26 June, 2015 Geometry of some functional architectures of vision Jean Petitot CAMS, EHESS, Paris J. Petitot Neurogeometry Bernard and visual neuroscience Bernard helped greatly the developement of geometrical models in visual neuroscience. In 1991 he organized the first seminars on these topics at the ENS and founded in 1999 with Giuseppe Longo the seminar Geometry and Cognition. From 1993 on, he organized at the Treilles Foundation many workshops with specialists such as Jean-Michel Morel, David Mumford, G´erard Toulouse, St´ephaneMallat, Yves Fr´egnac, Jean Lorenceau, Olivier Faugeras. He organised also in 1998 with J.-M. Morel and D. Mumford a special quarter Mathematical Questions on Signal and Image processing at the IHP. He worked with Alain Berthoz at the College de France (Daniel Bennequin worked also a lot there on geometrical models in visual neuroscience). J. Petitot Neurogeometry Introduction to Neurogeometry In this talk I would try to explain some aspects of Neurogeometry, concerning the link between natural low level vision of mammals and geometrical concepts such as fibrations, singularities, contact structure, polarized Heisenberg group, sub-Riemannian geometry, noncommutative harmonic analysis, etc. I will introduce some very basic and elementary experimental facts and theoretical concepts. QUESTION: How the visual brain can be a neural geometric engine? J. Petitot Neurogeometry The visual brain Here is an image of the human brain. It shows the neural pathways from the retina to the lateral geniculate nucleus (thalamic relay) and then to the occipital primary visual cortex (area V 1). J. Petitot Neurogeometry fMRI of human V1 fMRI of the retinotopic projection of a visual hemifield on the corresponding V1 (human) hemisphere.
    [Show full text]
  • The Retina the Retina the Pigment Layer Contains Melanin That Prevents Light Reflection Throughout the Globe of the Eye
    The Retina The retina The pigment layer contains melanin that prevents light reflection throughout the globe of the eye. It is also a store of Vitamin A. Rods and Cones Photoreceptors of the nervous system responsible for transforming light energy into the electrical energy of the nervous system. Bipolar cells Link between photoreceptors and ganglion cells. Horizontal cells Provide inhibition between bipolar cells. This is the mechanism of lateral inhibition which is important to edge detection and contrast enhancement. Amacrine cells Transmit excitatory signals from bipolar to ganglion cells. Thought to be important in signalling changes in light intensity. Neural circuitry About 125 rods and 5 cones converge on each optic nerve fibre. In the central portion of the fovea there are no rods. The ratio of cones to optic nerves in the fovea is one. This increases the visual acuity of the fovea. Rods and Cones Photosensitive substance in rods is called rhodopsin and in cones is called iodopsin. The Photochemistry of Vision Rhodopsin and Iodopsin Cis-retinal +Opsin Light sensitive Light Trans-retinal Opsin Light insensitive This is a reversible reaction Cis-retinal +Opsin Light sensitive Vitamin A In the presence of light, the rods and cones are hyperpolarized mv t Hyperpolarizing potential lasts for upto half a second, leading to the perception of fusion of flickering lights. Receptor potential – rod and cone potential Hyperpolarizing receptor potential caused by rhodopsin decomposition. Hyperpolarizing potential lasts for upto half a second, leading to the fusion of flickering lights. Light and dark adaptation in the visual system The eye is capable of vision in conditions of light that vary greatly in intensity The eye adapts dynamically to lighting conditions Light and Dark Adaptation We are able to see in light intensities that vary greatly.
    [Show full text]
  • Informing Computer Vision with Optical Illusions
    Informing Computer Vision with Optical Illusions Nasim Nematzadeh David M. W. Powers Trent Lewis College of Science and Engineering College of Science and Engineering College of Science and Engineering Flinders University Flinders University Flinders University Adelaide, Australia Adelaide, Australia Adelaide, Australia [email protected] [email protected] [email protected] Abstract— Illusions are fascinating and immediately catch the increasingly detailed biological characterization of both people's attention and interest, but they are also valuable in retinal and cortical cells over the last half a century (1960s- terms of giving us insights into human cognition and perception. 2010s), there remains considerable uncertainty, and even some A good theory of human perception should be able to explain the controversy, as to the nature and extent of the encoding of illusion, and a correct theory will actually give quantifiable visual information by the retina, and conversely of the results. We investigate here the efficiency of a computational subsequent processing and decoding in the cortex [6, 8]. filtering model utilised for modelling the lateral inhibition of retinal ganglion cells and their responses to a range of Geometric We explore the response of a simple bioplausible model of Illusions using isotropic Differences of Gaussian filters. This low-level vision on Geometric/Tile Illusions, reproducing the study explores the way in which illusions have been explained misperception of their geometry, that we reported for the Café and shows how a simple standard model of vision based on Wall and some Tile Illusions [2, 5] and here will report on a classical receptive fields can predict the existence of these range of Geometric illusions.
    [Show full text]
  • The Perception of Color from Motion
    UC Irvine UC Irvine Previously Published Works Title The perception of color from motion. Permalink https://escholarship.org/uc/item/01g8j7f5 Journal Perception & psychophysics, 57(6) ISSN 0031-5117 Authors Cicerone, CM Hoffman, DD Gowdy, PD et al. Publication Date 1995-08-01 DOI 10.3758/bf03206792 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Perception & Psychophysics /995,57(6),76/-777 The perception of color from motion CAROLM. CICERONE, DONALD D. HOFFMAN, PETER D, GOWDY, and JIN S. KIM University ofCalifornia, Irvine, California Weintroduce and explore a color phenomenon which requires the priorperception of motion to pro­ duce a spread of color over a region defined by motion. Wecall this motion-induced spread of colordy­ namic color spreading. The perception of dynamic color spreading is yoked to the perception of ap­ parentmotion: As the ratings of perceived motion increase, the ratings of color spreading increase. The effect is most pronounced ifthe region defined by motion is near 10 of visual angle. As the luminance contrast between the region defined by motion and the surround changes, perceived saturation of color spreading changes while perceived hue remains roughly constant. Dynamic color spreading is some­ times, but not always, bounded by a subjective contour. Wediscuss these findings in terms of interac­ tions between color and motion pathways. Neon color spreading (see, e.g., van Tuijl, 1975; Varin, Mathematica (Version 2.03) program used for generating 1971) shows that the colors we perceive do not always such frames is given in Appendix A.
    [Show full text]
  • Important Processes Illustrated September 22, 2021
    Important Processes Illustrated September 22, 2021 Copyright © 2012-2021 John Franklin Moore. All rights reserved. Contents Introduction ................................................................................................................................... 5 Consciousness>Sense .................................................................................................................... 6 space and senses ....................................................................................................................... 6 Consciousness>Sense>Hearing>Music ..................................................................................... 18 tone in music ........................................................................................................................... 18 Consciousness>Sense>Touch>Physiology ................................................................................ 23 haptic touch ............................................................................................................................ 23 Consciousness>Sense>Vision>Physiology>Depth Perception ................................................ 25 distance ratio .......................................................................................................................... 25 Consciousness>Sense>Vision>Physiology>Depth Perception ................................................ 31 triangulation by eye ..............................................................................................................
    [Show full text]
  • A Neural Model of the Scintillating Grid Illusion: Disinhibi- Tion and Self-Inhibition in Early Vision
    LETTER Communicated by Sidney Lehky A Neural Model of the Scintillating Grid Illusion: Disinhibi- tion and Self-Inhibition in Early Vision Yingwei Yu Downloaded from http://direct.mit.edu/neco/article-pdf/18/3/521/816498/neco.2006.18.3.521.pdf by guest on 24 September 2021 [email protected] Yoonsuck Choe [email protected] Department of Computer Science, Texas A&M University, College Station, Texas 77843-3112, U.S.A A stationary display of white discs positioned on intersecting gray bars on a dark background gives rise to a striking scintillating effect—the scin- tillating grid illusion. The spatial and temporal properties of the illusion are well known, but a neuronal-level explanation of the mechanism has not been fully investigated. Motivated by the neurophysiology of the Limulus retina, we propose disinhibition and self-inhibition as possible neural mechanisms that may give rise to the illusion. In this letter, a spa- tiotemporal model of the early visual pathway is derived that explicitly accounts for these two mechanisms. The model successfully predicted the change of strength in the illusion under various stimulus conditions, indicating that low-level mechanisms may well explain the scintillating effect in the illusion. 1 Introduction The scintillating grid illusion consists of bright discs superimposed on in- tersections of orthogonal gray bars on a dark background (see Figure 1A; Schrauf, Lingelbach, & Wist, 1997). In this illusion, illusory dark spots are perceived as scintillating within the white discs. Several important prop- erties of the illusion have been discovered and reported inrecent years. (1) The discs that are closer to a fixation show less scintillation (Schrauf et al., 1997), which might be due to the fact that receptive fields in the periphery are larger than those in the fovea.
    [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]
  • Subject Index
    Subject Index Absence, 47, 79, 83, 87, 89, 131, 143, 204, Appearances, 8, 10, 11, 17, 19, 51, 96, 112, 227, 230, 232, 265, 267, 268, 271, 272, 279, 121, 123, 127, 128, 130, 159, 162, 180, 315, 317, 318, 320–325, 354, 373 184–192, 224, 242, 261, 288, 289, 292, Abstraction, 6, 172, 174, 176, 178, 187, 194, 322–325, 335, 350–352, 356, 357, 359, 361, 338, 354, 368, 369, 373, 375, 400, 402, 404, 365, 373, 406 412 Art, 17, 20, 31, 93, 131, 338, 399–404, 411– Accident, 128, 144, 145, 189, 204, 212, 213, 420 234, 360, 364 abstract art, 20, 401–405, 411, 412 Accommodation, 203, 211, 224–226 color, 402, 403–404 Action-perception synergies, 131, 132, 133 compositional techniques, 399–404 Activation zone, 375 constructivism, 396, 398, 406, 407, 412, Active vision, 131 418 Adaptive strategies, 85, 96, 97 generative art, 20, 411, 412, 414–418 Additive scanning, 364 history, 184, 393 Aesthetics, 2, 9, 16, 17, 85, 90, 91, 93, 97, 113, modulation, 83, 402–403 121, 413 Pop/Op, 31, 113, 124, 352 Affine distortion, 220, 223 Artificial intelligence, 1, 28, 31 Affordance, 14, 15, 186, 338, 356, 359 Artistic expression, 83, 85, 90, 91, 97 Afterimage, 112, 149, 150 Astigmatism, 112 Alphabet, 271, 347, 351, 367 Attention, 6, 51, 84, 96, 99, 100, 125, 174, Amodal, 47, 315, 336 190, 355, 356, 375, 376, 394, 396, 397 boundaries, 263, 266 Attneave points, 5, 125, 129 completion, 175, 261, 265, 270, 273, 315, Auditory objects, 340 318, 322–324, 328, 329, 374, 376 Auffälligkeit, 375 contours, 8, 15, 19, 263, 280 Automatic processes, 4, 32, 85, 96, 97, 100, perception,
    [Show full text]
  • Arxiv:1907.09019V2 [Cs.CV] 5 Aug 2019
    Preprint IMAGENET-TRAINED DEEP NEURAL NETWORK EX- HIBITS ILLUSION-LIKE RESPONSE TO THE SCINTILLAT- ING GRID Eric Sun Ron Dekel Department of Physics Department of Neurobiology Department of Chemistry and Chemical Biology Weizmann Institute of Science Harvard University Rehovot, PA 7610001, Israel Cambridge, MA 02138, USA [email protected] eric [email protected] ABSTRACT Deep neural network (DNN) models for computer vision are now capable of human-level object recognition. Consequently, similarities in the performance and vulnerabilities of DNN and human vision are of great interest. Here we charac- terize the response of the VGG-19 DNN to images of the Scintillating Grid visual illusion, in which white dots are perceived to be partially black. We observed a significant deviation from the expected monotonic relation between VGG-19 rep- resentational dissimilarity and dot whiteness in the Scintillating Grid. That is, a linear increase in dot whiteness leads to a non-linear increase and then, remark- ably, a decrease (non-monotonicity) in representational dissimilarity. In control images, mostly monotonic relations between representational dissimilarity and dot whiteness were observed. Furthermore, the dot whiteness level correspond- ing to the maximal representational dissimilarity (i.e. onset of non-monotonic dissimilarity) matched closely with that corresponding to the onset of illusion per- ception in human observers. As such, the non-monotonic response in the DNN is a potential model correlate for human illusion perception. 1 INTRODUCTION Deep neural network (DNN) models are capable of besting human champions in chess [18] and Go [20] and reaching superhuman levels of accuracy in image classification and object recognition tasks [3, 11, 5, 18].
    [Show full text]
  • Book XVII License and the Law Editor: Ramon F
    8 88 8 8nd 8 8888on.com 8888 Basic Photography in 180 Days Book XVII License and the Law Editor: Ramon F. aeroramon.com Contents 1 Day 1 1 1.1 Photography and the law ....................................... 1 1.1.1 United Kingdom ....................................... 2 1.1.2 United States ......................................... 6 1.1.3 Hong Kong .......................................... 8 1.1.4 Hungary ............................................ 8 1.1.5 Macau ............................................. 8 1.1.6 South Africa ......................................... 8 1.1.7 Sudan and South Sudan .................................... 9 1.1.8 India .............................................. 10 1.1.9 Iceland ............................................ 10 1.1.10 Spain ............................................. 10 1.1.11 Mexico ............................................ 10 1.1.12 See also ............................................ 10 1.1.13 Notes ............................................. 10 1.1.14 References .......................................... 10 1.1.15 External links ......................................... 12 2 Day 2 13 2.1 Observation .............................................. 13 2.1.1 Observation in science .................................... 14 2.1.2 Observational paradoxes ................................... 14 2.1.3 Biases ............................................. 15 2.1.4 Observations in philosophy .................................. 16 2.1.5 See also ...........................................
    [Show full text]
  • Use of the Hermann Grid Illusion in the Measurement of Contrast Perception in Dyslexia
    CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector Vision Research 45 (2005) 1–8 www.elsevier.com/locate/visres Rapid communications Use of the Hermann grid illusion in the measurement of contrast perception in dyslexia James M. Gilchrist a,*, Barbara K. Pierscionek b, William M. Mann a a Department of Optometry, University of Bradford, Richmond Road, Bradford, BD7 1DP West Yorkshire, UK b School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK Received 12 March 2004; received in revised form 28 July 2004 Abstract We measured contrast thresholds for perception of the Hermann grid illusion, using different contrast polarities and mean lumi- nances, in dyslexics and non-dyslexics. Both groups of subjects gave significantly lower thresholds with grids having dark squares and light paths, but there was no significant threshold difference between groups. Perceived strength of illusion was also measured in grids at suprathreshold contrast levels. Dyslexics perceived the illusion to be significantly stronger than non-dyslexics when the grid had light paths and low luminance. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Dyslexia; Contrast perception; Hermann grid; Magnocellular 1. Introduction (Livingstone, Rosen, Drislane, & Galaburda, 1991) and psychophysical studies which indicate that some Dyslexia has been defined as a specific reading diffi- dyslexics suffer reduced sensitivity to contrast, flicker culty, inexplicable by any deficit in intelligence, learning and/or motion (Cornelissen, Richardson, Mason, & opportunity, motivation or sensory acuity (Critchley, Stein, 1995; Demb, Boynton, Best, & Heeger, 1998; 1970). The signs of dyslexia are varied and include Everatt, Bradshaw, & Hibbard, 1999; Lovegrove, abnormal phonological awareness, difficulties with writ- 1991; Lovegrove, Bowling, Badcock, & Blackwood, ing, spelling, auditory discrimination and visual process- 1980).
    [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]