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Induced movement occurs not only when an object surrounding a stationary one moves below threshold but when it moves above threshold. The above-threshold effect is particularly puzzling and seemingly irrational because the relative displacement should be fully accounted for by perceiving the moving object in motion. The accepted theory has been that such excess motion can be explained in terms of a separation of systems: The enclosed object is governed by the relationship to its immediately surrounding frame of reference, and the latter is governed either by the relationship to its surrounding frame of reference or to the observer. An alternative explanation is that when induced motion occurs, the moving object is perceived to be either stationary or moving less than is warranted by its actual motion. Evidence is presented supporting this hypothesis according to which the relative displacement is apportioned phenomenally to either the induced object, the inducing object, or both. The objective motion of the inducing object is thus in whole or part transferred to the induced object. Thus, excess phenomenal motion does not occur, and induced movement can be regarded as the rational solution to a problem.As with many phenomena of perception, induced movement has been studied experimentally over many decades, but there is little agreement as to its explanation. There is agreement that the displacement of one object relative to another (object-relative displacement) is an important source of information concerning motion. If one object is moving at a rate below threshold, the introduction of a second stationary object leads to an immediate impression of motion, and this impression must logically be based on relative displacement (Duncker, 1929;Wallach, 1959Wallach, ,1976. Moreover, the stationary object will be seen in motion as often as the actually

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When a figure moves behind a narrow aperture in an opaque surface, if it is perceived as a figure, its shape will often appear distorted. Under such anorthoscopic conditions, the speed or direction of the object's motion is ambiguous. However, when the observer simultaneously tracks a moving target, a figure is always perceived, and its precise shape is a function of the speed or direction of tracking. The figure is seen as moving with the speed or in the direction of the target. Thus, it is argued that eye movement serves as a cue to the figure's motion, which, in turn, determines its perceived length or orientation.