The influence of both visual texture density gradients and object familiarity on relative size and distance judgments.

Various hypotheses derived from Gibson's psychophysical theory of perception are experimentally tested. Results show that judgments of the relative physical sizes and relative physical distances of objects, made over variously textured surfaces, are strongly influenced by the texture density gradients of stimulation, derived from the surfaces. Results, however, also indicate that, in isolation, the monocular stimulation gradient of texture density cannot supply observers with sufficient "stimulus information" to enable their phenomenal judgments of the spatial ordering of the environment to accord exactly with the actual physical dimensions of the environment. Despite the presence of well defined texture density gradients of stimulation, Ss' judgments of both the relative physical sizes and the relative physical distances of objects are influenced by, theoretically incidental, extraneous stimuli. Ss' judgments also show variations under conditions of monocular or binocular vision. Ss' judgments of the relative physical distances of certain objects are shown to be significantly related to their judgments of the relative physical sizes of these objects, in accordance with predictions derived from the "Size-Distance Invariance Hypothesis." Despite the presence of a well defined texture density gradient of stimulation, relative differences in the retinal image sizes of various objects are seen to influence judgments of the relative distances of the objects, both when the objects are dissimilar in shape and, even when Ss are not manipulatively familiar with the objects. Results are discussed in relation to Gibson's theory (considered as a "cue theory" of perception). Several directives for future research projects are suggested. In particular, results of a preliminary investigation indicate that following a period of "texture deprivation", during which translucent goggles are worn, Ss become more responsive to textural factors in the environment. It is suggested that specific forms of sensory deprivation may create specific types of "stimulus hunger.".