The independence of size perception and distance perception

Research on distance perception has focused on environmental sources of inf ormation, which have been well documented; in contrast, size perception res earch has focused on familiarity or has relied on distance information. An analysis of these two parallel bodies of work reveals their lack of equival ence. Furthermore, definitions of familiarity need environmental grounding, specifically concerning the amount of size variation among different token s of an object. To demonstrate the independence of size and distance percep tion, subjects in two experiments were asked to estimate the sizes of commo n objects from memory and then to estimate both the sizes and the distances of a subset of such objects displayed in front of them. The experiments fo und that token variation was a critical variable in the accuracy of size es timations, whether from memory or with vision, and that distance had no imp act at all on size perception. Furthermore, when distance information was g ood, size had no effect on distance estimation; in contrast, at far distanc es, the distances to token variable or unknown objects were estimated with less accuracy. The results suggest that size perception has been misconcept ualized, so that the relevant research to understand its properties has not been undertaken. The size-distance invariance hypothesis was shown to be i nadequate for both areas of research.