Assumptions relating an individual to the informational structure of his environment

Abstract

Human beings have a number of assumptions that reflect the structure of the physical world that we have been discussing. These assumptions are normally tacit, deeply rooted, universal and compelling. Their operation can be detected particularly in illusions. Thus there is the universal assumption that the sky at the horizon is further away than the sky above. This leads to the moon looking larger on the horizon. Even when one knows that the moon on the horizon is actually no further away than the moon at its zenith, the illusion persists (Kaufman and Rock, 1962). In the perception of depth as determined by shadows (as in relief photographs) there is the equally universal and com­pelling assumption that the light source is above the surface. Thus for exam­ple a human face lighted from below produces a sense of strangeness and un­naturalness (Hess, 1961). Assumptions of this kind appear to prevail in all the ways in which the human organism handles information from the en­vironment. Typically, the existence of these assumptions would make no biological sense if it were not for the fact that they represent adaptation to the persistent and pervasive characteristics of the external environment. Thus, as Ptolemy correctly observed about the moon illusion, the space between us and the horizon is typically filled with things and places for things; the space above us is generally empty. Similarly most occasions are illuminated by the sun, the moon or starlight, all of these enter our world from outside, from above. The adaptive nature of many of these assumptions has been positively established by experiments.