  A primary disagreement between computational and ecological psychologists concerns the nature of the stimuli to which organisms are exposed. Computationalists largely regard these stimuli as, in Chomsky’s terminology, impoverished (Chomsky 1980). The linguistic utterances to which an infant comes in contact do not, on their own, contain sufficient information to indicate the grammar of a language. Similarly, the visual information present in the light that stimulates an organism’s retina does not, on its own, specify the layout of surfaces in the organism’s environment. Visual perception faces an “inverse optics” problem. For any pattern of light on a retina, there exists an infinite number of possible distal surfaces capable of producing that pattern. The visual system thus seems to confront an impossible task—while it is possible to calculate the pattern of light a reflecting surface will produce on the retina, the inverse of this problem appears to be unsolvable, and yet visual systems solve it all the time and, phenomenologically speaking, immediately.