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The Senses Considered As Perceptual Systems· The Senses Considered as Perceptual Systems· JAMES J. GIBSON Cornell University London GEORGE ALLEN & UNWIN LTD RUSKIN HOUSE MUSEUM STREET Editor's Foreword How do animals, including human beings; secure the information from the world about them that is essential to their adaptation to it and their survival in it? Since ancient times this all-important question has been asked in many ways and a great variety of answers have been proposed. In this book the basic problem is analyzed anew and solutions are sug- gested which are both scientifically satisfying and almost startlingly novel. Dr. Gibson does not treat of the different senses as mere producers of visual, auditory, tactual, or other sensations. Rather, he regards them as active seeking mechanisms for looking, listening, touching, and the like. This means that the emphasis is on explanations of how we are able to have the constant perceptions that we need for effective action and avoidance of physical harm in our everyday lives. The author clearly supports his view that the perception of reality is not something as- sembled or computed by the brain from an ever-varying kaleidoscope of sensations. Dr. Gibson emphasizes the importance of regarding the different per- ceptual systems not only as active, but also interrelated. He points out that visual perception, for example, is frequently a seeking of informa- tion by head and eye movements coordinated in the so-called eye-head system. Similar active adjustments take place as the organism secures information with its ear-head system. The same can be said of the seek- ing and searching of the hand-body system. These out-reaching mech- anisms search out for the organism the required perceptual information about the world in which it exists. This dynamic perception is contrasted with the quite different sensory experience that results from the activation of essentially passive receptors. As the author notes, sensory experiences resulting from passive stimula- tion, that is, simple receptor activation, have been very widely studied in laboratories of physiology and psychology, with rigorous control of both the stimulus energies presented to the organism and the receptor cells that are acted upon. Dr. Gibson acknowledges these sensory experiences as facts, but he treats them as by-products of perception rather than building blocks. In other words, this book is not just another treatise on the anatomy and physiology of receptors. It is not a new report on quantitative experi- v vi / EDITOR'S FOREWORD mental findings of sensory thresholds. It is not an essay on psychophysics. It is even not directly concerned with the sensory projection areas of the brain or with the coding of impulses in afferent peripheral nerves. Rather, it has quite another mission, all too often neglected or forgotten. It ex- plains how our senses, as active interrelated systems, provide continuous, stable information that alone makes adaptive living possible. Successive chapters embrace the contribution made by each of the main receptor systems that are basic to the adjustment of the organism to its world. To me, the author's thesis seems most arresting in his daring, yet convincing new look at the psychological functions of the total visual mechanism. He introduces the concept of "ecological optics." This new treatment is not mentalistic; it is not traditionally physiological or physi- cal; but it is still rigorously scientific. In terms of this novel point of view, the book examines some fundamental questions in psychology: What is innate and what is acquired in perception? What is the role of learning in establishing adult perception? How is perceiving related to expec- tancy? What is the effect of language on perceiving? What are per- ceptual illusions? All in all, the editor considers this novel and challenging book a most important contribution to the assumptions underlying all scientific con- cern with living animals, especially human beings. In some respects it amplifies and develops ideas that were first presented in the author's earlier book, The Perception of the Visual World (Allen and Unwin, 1952). That book has received wide acceptance and has sparked many continuing fruitful experimental programs. An acquaintance of the editor, one of England's ablest psychologists, said of that earlier book that it seemed to him the most insightful volume to come from American psy- chology for decades. Certainly this new book merits similar praise. I have no doubt it will be forthcoming. It is refreshingly novel in the solutions it proposes for some of the oldest and most fundamental problems. Certainly not all professional students of mental life will agree with all the conclusions of this book. But it will be a brave psychologist indeed who feels he can afford to be ignorant of what is said in it. Leonard Carmichael Preface This book has had to be written twice - once in 1958-59 and again in 1963-64. The second draft is more explicit and coherent than the first, for a good deal of experimenting, teaching, arguing, reading, and re- formulating came in between. I needed to restudy the theories of per- ception handed down from the philosophers of the seventeenth and eighteenth centuries - theories that were only slightly modified by the experimental psychologists of the nineteenth and twentieth centuries. I also had to survey the whole area of the anatomy and physiology of the senses. It was difficult to shake off the traditional explanations of the facts while keeping hold of the facts themselves. I am very grateful to the Institute for Advanced Study in Princeton for taking me in and then leaving me alone while the first draft was being written. The Center for Advanced Study in the Behavioral Sciences shel- tered me during the second draft, and that year was a real pleasure. These admirable establishments have made this book possible. And if the National Institutes of Health had not granted Cornell one of their career research awards on my behalf, the book would not be finished yet. A series of experiments lies behind the writing of this book. These studies, published and unpublished, have been supported for many years by the Physiological Psychology Branch of the Office of Naval Research under a contract with Cornell (Nonr 401-14). This agreement is for work on the perception of "motion" and of "space." The justification for such support has been that clarification of these ancient puzzles might contribute to aviation - and so it will someday. These chapters have been read in various versions and parts by a con- siderable number of knowledgeable persons, and to them I am indebted. The ones who gave the greatest help in revision were Leonard Car- michael, Wendell Gamer, Lloyd Kaufman, and T. A. Ryan. In formula- tion there are many others who helped, especially Julian Hochberg, who helped by arguing with me (or sometimes even agreeing) and thereby lessened the obscurity that the reader must face. The three experimental investigators in the field of perception who seem to be working closest to the vein of evidence that I am trying to mine are all from outside this country. They are Ivo Kohler of Innsbruck, Gunnar Johansson of Uppsala, and the late Albert Michotte of Louvain. vii viii / PREFACE Their discoveries are invaluable and, however the facts are interpreted, crucial for any theory of sense perception. Psychologists of the previous generation to whom lowe the greatest intellectual debt are E. B. Holt, Kurt Koffka, L. T. Troland, and E. G. Boring. This is a mixed group, but the fact is that I am attempting to reformulate stimulus-response theory, Gestalt phenomenology, and psy- chophysics so as to extract new theorems from these old theories. Above all, I am indebted to my students. A teacher depends on his students as much as they do on him. The young psychologists to whom lowe most are John Hay, Jacob Beck, Howard Flock, William Schiff, Horace Reynolds, Anne Danielson Pick, and Herbert Pick. This whole inquiry has been shared for years with Eleanor J. Gibson, my wife. In 1963, however, we divided the problems between us, and she has concentrated on perceptual learning and development while I concentrated on the senses. Her forthcoming book will take up the story where mine leaves off. Ithaca, New York J. J. G. April 1966 Contents Introduction I What are the senses? 1/ The Senses and the Sensory Nerves 4/ The Improvement of Perception with Learning 5/ The Facts to be Surveyed 6/ I The Environment as a Source of Stimulation 7 The Terrestrial Environment 8/ The Consequences of Rigidity 8/ The Consequences of Gravity 10/ The Conse- quences of Electromagnetic Radiation 11/ The Special Consequences of Light 12/ The Air as a Medium 14/ Ambient Information 15/ Perspective Projections of an Object 15/ Compression Waves from a Vibratory Event 15/ The Diffusion of Volatile Substances 17/ Chemical Contacts with the Environment 19/ Mechanical Contacts with the Environment 20/ The World of Physics and the Sources of Stimulation 21/ The Animate Environment 22/ Social Stimulation 23/ Social Interaction 24/ The Environment of Emerging Man 24/ The Cultural Environment 26/ The Meaning of the Term "Stimulus" 28/ Summary 29/ II The Obtaining of Stimulation 31 Two Ways of Obtaining Stimulation 32/ The Fallacy of Ascribing Proprioception to Proprioceptors 33/ The Lower Proprioceptive Systems: Posture and Equilibrium 35/ The Higher Proprioceptive Systems: Purposive Action 36/ Theories of Action Sensitivity 38/ The Characteristics of a Natural Stimulus 39/ Receptors,
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