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Perception and Illusion Historical Perspectives Library of the History of Psychological Theories SeriesEditor:RobertW.Rieber,CityUniversityofNewYork,NewYork,NY PERCEPTIONANDILLUSION HistoricalPerspectives NicholasJ.Wade AcontinuationOrderPlanisavailableforthisseries.Acontinuationorderwillbringdelivery ofeachnewvolumeimmediatelyuponpublication.Volumesarebilledonlyuponactual shipment.Forfurtherinformationpleasecontactthepublisher. Perception and Illusion Historical Perspectives Nicholas J. Wade UniversityofDundee Dundee,UnitedKingdom Springer eBookISBN: 0-387-22723-7 Print ISBN: 0-387-22722-9 ©2005 Springer Science + Business Media, Inc. Print ©2005Springer Science + Business Media, Inc. Dordrecht All rights reserved No part of this eBook maybe reproducedor transmitted inanyform or byanymeans,electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Springer's eBookstore at: http://ebooks.kluweronline.com and the Springer Global Website Online at: http://www.springeronline.com ToDaisyandSam This page intentionally left blank Preface Ourcontactwiththeworldisthroughperception,andthereforethestudy of the process is of obvious importance and significance. For much of its long history, the study of perception has been confined to naturalis- tic observation. Nonetheless, the phenomena considered worthy of note have not been those that nurture our survival—the veridical features of perception—but the oddities or departures from the common and com- monplaceaccuraciesofperception.Withthemovefromthenaturalworld tothelaboratorytheodditiesofperceptionmultiplied,andtheyreceived evermoredetailedscrutiny. Mygeneralintentionistoexaminetheinterpretationsofthepercep- tualprocessanditserrorsthroughouthistory.Theemphasisonerrorsof perception might appear to be a narrow approach, but in fact it encom- passesvirtuallyallperceptualresearchfromtheancientsuntilthepresent. The constancies of perception have been taken for granted whereas departures from constancies (errors or illusions) have fostered fascination. Philosophicalapproachestoperceptionhavebeenbasedonobservations, anditisthelatterthatareattheforefrontofthepresentbook.Themeth- odsofrecordingobservationshavebecomemorerefined,butthishasnot resulted in an increased concern with veridicality. Rather, the range of illusions that are studied has exploded. Illusions in this context refer to perceptualdeparturesfromveridicality,ratherthantheconstrainedvari- etyofgeometrical-opticalillusionsthatsprangforthinthelatenineteenth century.Anystudyofillusionsispredicatedonanassumptionofastan- dardfromwhichtheerrorscanbeassessed.Thestandardsthemselveshave changedoverthecenturies,largelyasaconsequenceofdevelopmentsin thephysicalandlifesciences.Accordingly,thenatureofperceptualerror willitselfbeexaminedbeforesurveyingtheseen. Thus,myintentionistotreatperception,andprincipallyvision,asan observationaldiscipline.Recordingtheconsequencesofperceptionstarted vii viii PREFACE long before written reports were kept, and so art will be encompassed within this purview. Writers have remarked on their own visual experi- encessincewritingwasinvented,sothatalargebodyofobservationshas accumulated. This body is dissected in the present volume. Descriptions of visual experience are likely to be anchored in a more solid environ- mentthanthetheoriesproposedtoaccountforthembecausethetheories themselves have been dependent upon concepts derived from other dis- ciplines. The function of vision is to guide our behavior, and in so far as this guidance is successful, there might seem to be little in the subject to warrantenquiry.Indeed,theeternallyentertainedtheoryofnaiverealism speaks to this issue—the world is as it is perceived. Nonetheless, there were circumstances in which the phenomena of vision were remarkable andremarkedupon.Visualexperiencesindarkness(asaconsequenceof pressure or a blow applied to the eyeball) were not only remarked upon around 500 B.C., but they could have provided the phenomenal source foremissiontheoriesofvision—thatlightissuesfromtheeyeitself.Such theories might seem fanciful to us now, but the phenomena upon which they are based are as readily experienced today as they were two and a half thousand years ago, and descriptions of them have been repeatedly refined throughout that period. Afterimages provide a similar example; theycanbeseenfollowingexposuretobrightlight,theytakeontheshape oftheintensestimulus,andtheylingerforanappreciabletime.Theycould haveacted,togetherwiththereflectionsseeninwaterandintheeye,asa basisforthebeliefthatvisionwasmediatedbyimagesorcopiesofexternal objects. These phenomena and many others require an interpretation by any adequate theory of vision; the theories might be supplanted but the phenomenaremain. Science involves recording and interpreting natural phenomena. Nowadays, the records are the results of experiments and the many and variedphenomenaarepositedinwell-definedcompartments,likephysics, physiology, and psychology. These compartments are a relatively recent convention,asarethespecialistswholaborundertitlessuchasphysicists, physiologists, and psychologists. Neither the phenomena nor the practi- tionersweresoclearlydefinedinthedistantpast.Inantiquityscience,if such it should be called, was based upon describing and classifying ob- servations of naturally occurring events. The sense of science was sight, andvisionitselfwasanintegralpartofthedevelopmentofscience.What wasseencouldbedescribed,cataloged,andevensubjectedtomathemat- ical analysis. Plato’s approach to natural phenomena, however, did not encourage the observational analysis of vision, because of his distrust of the evidence of the senses: the world of appearances was considered to be a world of illusions, and the essence of thought was to be sought in PREFACE ix mathematicsandidealforms.Plato’sidealismremainedadominantforce inbothscienceandphilosophy.Hispreferenceformathematicsovermatter influencedEuclid,whoformulatedatheoryofvisioningeometricalterms, withlittleconcernforperceptualexperienceitself.Theseapproachestovi- sion contrasted sharply with that of Aristotle, who placed more reliance ontheevidenceofhissensesthanonphilosophicalspeculations. The phenomena most intimately involved with vision were those of light. Indeed, the distinction between light and sight was not seriously entertaineduntilKeplerdescribedtheopticalpropertiesoftheeye,early in the seventeenth century. Before Kepler, vision was essential to optics, anddisordersofvisionprovidedmaterialsformedicine.Accordingly,his- tories of optics and ophthalmology have focused on vision during their early phases, but have tended to subordinate it when either the physical natureoflightwasestablishedorthedioptrics,anatomy,andphysiology oftheeyewerebetterunderstood.Interpretationsoftheperceptualprocess continuetoevolveandthepresentsurveywillconsiderdevelopmentsin thetwentiethcenturyaswellasthosefromearliertimes. The book reflects various strands of historical reseach in perception thathaveexcitedmyinterest.Theseinterestshavebeensharedwithoth- ers, to whom thanks are due. Mike Swanston, Mike Cowles, Hiro Ono, Helen Ross, Stan Finger, Dieter Heller, Ben Tatler, Frans Verstraten, and Alan Wilkes have all helped to shape my thoughts regarding historical issues. The errors that survived their shaping should not, of course, be associated with them but must reflect my reluctance to follow more ap- propriatelinesofenquiry.Mygreatestsupporthasderivedfrommywife, Christine.However,itisnottoherthatthebookisdedicated,buttoour twonewgrandchildrenbornduringitswriting.