Depth Adjacency and Induced Motion

Induced motion was investigated as a function of the stereoscopic separation of the test and inducing object and the instructions to attend to or to ignore the inducing object. It was found that stereoscopically displacing the test object from the inducing object with both kinds of instructions resulted in a decrease in the magnitude of induction particularly with crossed disparity. These results are consistent with the adjacency principle and with the ability of attention as well as adjacency to modify the magnitude of the induced motion.

Relative Motion and the Adjacency Principle

The perception of motion of physically moving points of light was investigated in terms of the distinction between absolute and relative motion cues and the change in the effectiveness of the latter as a function of the frontoparallel separation between the points. In situations in which two competing relative motion cues were available to determine the perceived path of motion of a point of light, it was found that the relative motion cue between more adjacent points was more effective than the relative motion cue between more separated points. In situations in which only one relative motion cue was available to determine the perceived motion of a point it was found that the effectiveness of this cue as compared with the absolute motion cue decreased with increased separation. These results are predictable from the adjacency principle which states that the effectiveness of cues between objects is an inverse function of object separation. Some consequences of the study for the theory of motion perception are discussed.

Depth Distortions in Binocular Fields

The introduction of misleading size cues between binocularly presented objects can result in a distortion of the binocular visual field. The effect of this primary distortion upon the perceived depth of extraneous objects (objects not used in generating the primary distortion) was studied when both the primary distortion and the extraneous objects involved vertical separations. It was found that the perceived depth between the extraneous objects (the secondary distortion) was affected by the presence of the primary distortion. From the present and previous studies it can be concluded that the secondary distortion is directly related to the primary distortion for either horizontal or vertical separations of the objects in both the distortions. This result is discussed as an example of the “adjacency principle.”