The construction of visual reality

Abstract

This chapter examines the standard definitions of illusion and hallucination. These definitions assume a standard theory of perception in which a goal of perception is to estimate true properties of an objective physical world. This standard theory of perception is usually justified on evolutionary grounds: Those creatures that see more truly are ipso facto more fit. However, a closer examination of perceptual evolution using the tools of evolutionary game theory reveals that this standard assumption is incorrect. Perception has not evolved to report truth, but instead to guide adaptive behavior within a niche. In this regard, our perceptions are much like the windows desktop of a computer, which serves to guide useful interactions with the computer while sparing the user from having to know the truth of its structure and function. This understanding of perceptual evolution requires us to replace the standard definitions of illusion and hallucination with new ones that better reflect the central role of perception as a guide to adaptive behavior.