Some Comments on J. J. Gibson's Approach to Picture Perception

Abstract

In his recent writings James J. Gibson has been quite liberal with descriptions of the confusion, the errors, the ignorance and the irrelevance of what he finds around himself in his field of interest. He has made me, for one, the more eager to receive the final enlightenment, which, according to him, is just around the corner. But if the chapter published in Leonardo [1] is characteristic of his forthcoming book, I am in for another disappointment. Those of us who waited all those years for Gibson to overcome the naive notion that pictures are duplicates of their referents, must be forgiven if they are less dazzled by his recent revelations than he is himself. How a seasoned researcher could be satisfied with undefined and vague concepts such as 'information' or 'invariants' is a mystery. He surely cannot expect many readers to be content with statements such as: 'The invariants are not abstractions or concepts. They are not knowledge: they are simply' invariants' [ 1]. If, then, I try to extract the meaning of his 'invariants' from his examples, I find that it derives from the constancy of shape. He calls his presentation of this phenomenon 'a very radical hypothesis', even though the constancy of shape became a common property of psychology textbooks in 1935, at the latest, when Kurt Koffka in his Principles of Gestalt Psychology devoted a chapter to the visual constancies [2]. The term 'constancy of shape' concerns the observation that in daily life people frequently see the objects of their environment with some of the spatial properties the objects possess in the physical world rather than with those of their projective images. A brick, for example, retains its right-angle shape and objective proportions, no matter from where one looks at it. (The observation applies, however, only to simple, regular shapes. It works for a brick but not, for example, for complex sculptures that change their angles and proportions continuously as one walks around them.) Drawing attention to the constancies was only the beginning of the work that had to be done. The principal task of psychologists was to explain the phenomenon-that is,they had to describe its causes and the mechanisms that made it work. It is