Absolute motion parallax and the specific distance tendency

In the absence of definitive cues’to distance, the perceived distance of an object will be in error in the direction of the object appearing at a distance of about 2 m from O. This tendency to perceive an object at a relatively near distance is termed the specific distance tendency (Gogel. 1969). Also, it has been found that an error in perceiving the distance of an object will result in an apparent movement of the object when the head is moved (Hay & Sawyer. 1969; Wallach, Yablick. & Smith. 1972). From these two results, it was expected that the direction of trie apparent movement of a stationary point of light resulting from head movement would vary predictably as a function of the physical distance of the point of light from O. This expectation was confirmed in an experiment in which both the perceived motion and perceived distance of the point of light were measured. The consequences of the study for the role of motion parallax in the perception of distance and for the reafference principle in the perception of object motion with head motion are discussed