Perceived target displacement as a function of field movement and asymmetry

In two experiments induced movement of an object was produced to demonstrate that movement of the background influences the perceived localization of the object in space. The Roelofs (asymmetry) effect could be used to explain only part of the shift in localization in Experiment1. The asymmetry effect was excluded from Experiment2 by the procedure employed. It was concluded that the Roelofs effect is a sufficient, but not necessary, condition for the effects of induced movement to occur, and that relative displacement of the target and background plays an important part in the illusion. Furthermore, it was shown that the effects of induced movement can occur even when the border of the background remains stationary.