Instruction effects on size and distance judgments.

Abstract

The hypotheses that size judgments of unfamiliar objects are affected by distance informa­ tion, and distance judgments by size information, were tested. Subjects made size or distance estimates in a cue-reduced situation, with or without distance or size information, and also made calibrated estimates in full-cue conditions. Size judgments in the no-information condition were correlated with the retinal image, whereas distance information produced size estimates closer to the actual size of the objects. Subjects given no information about size produced dis­ tance estimates that were randomly distributed, whereas size information yielded a weak effect in the appropriate direction. Implications for the size-distance invariance hypothesis and the specific distance tendency are discussed. No previous investigation has assessed both the effects of size information on distance judgments and the effect of distance information on size judg­ ments for varying retinal images. The purpose of the present study was to investigate these variables in a single experimental setting in which cue reduction was assured. The majority of the studies in this area focus on size or distance judgments under familiar size in­ structions or with off-sized familiar objects. Several studies (Fitzpatrick, Pasnak, & Tyer, 1982; Gogel, 1968; Gogel & Mertens, 1967) have shown that the judged size of a familiar object corresponds very well to its real size, and judged distance corresponds to the actual distance at which that size would produce the given retinal size. In other studies (Baird, 1963; Park & Michaelson, 1974), an object is presented and the observer is told that it is the same size as a fa­ miliar object; distance judgments correspond quite well to the distance at which that object would pro­ duce the given retinal image. It is not clear what the effect would be if an instruc­ tion regarding an object's size was not associated with a familiar object. In this case, an observer would have to interpret the object in terms of the retinal image and cognitive information. Coltheart (1970) reported that subjects could do this very well; Park and Michaelson (1974), on the other hand, reported that size instruction had no effect on dis­ tance judgments. Since it is not possible to determine why these results differ, the present experiment was undertaken, in part, as an attempt to resolve this con­ flict.