Amoolya Chengalasetty¹ (), Jhera Darefsky¹, Albert Yonas¹; ¹Arizona State University

Familiar size is a pictorial depth cue for which an object's known physical size and visual angle influence observations of apparent distance. There is controversy over the type of process that accounts for the reports of depth. There is also controversy on the question of the effectiveness of this cue (. According to Gogel (1976), a non-perceptual cognitive process occurs when the observer experiences a display larger or smaller than a familiar object, such as off-size. The viewer judges that the object is closer or farther away than its perceived distance. To test this notion, Google had his participants move their heads to see if the apparent depth generated motion parallax. He found that the displays generated slight illusory motion parallax when observers moved laterally. Using realistic larger and smaller versions of Rubik’s Cubes and dice, Culham has recently reported that familiar size affects the actual distance of the display even in the presence of conflicting information from stereopsis. We created sets of novel objects that varied in size but were identical in shape and color. Twenty-two college students were familiarized with a smaller or larger version of three objects and asked to judge its apparent distance by moving a rod viewed with both eyes. After apparent depth was reported, the rod was placed at the same distance as the familiarized object, and the observer moved their head back and forth. Perception of motion of the object toward and away from the rod that was concomitant with the motion of the head was found on trials in which a large depth illusion was reported. On trials with little depth effect was observed, subjects reported no apparent motion. Apparent motion supports the view that familiar size is a perceptual illusion, and when it is sufficiently compelling, it can create apparent motion.