ABSTRACT
One of the earliest and also most influential theories about perception and perceptual development was the theory of H. von Helmholtz, the nineteenth-century German physicist and physiologist, who through his work on the sensory systems also became interested in the psychology of perception. The major exception was Jean Piaget, a Swiss psychologist, whose massive body of work on children is very well known. One particular innovation in his theory of perceptual development, clearly described in his book The Mechanisms of Perception, was the suggestion that at some stage in his life the child begins to use deductive inferences in order to make many of his perceptual judgements. The perceptual theories of Helmholtz and of Piaget use the idea of perceptual inferences extensively, and the Gestalt theory of perception, although not directly concerned with the issue, did, it can be argued, establish one very good reason why inferences are necessary.
