Illusory motions induced by rapid displacements of the observer.

Some illusory effects of movement are described that are easily observable when the subject is in rapid locomotion (driving a car or travelling on a train) and gazes fixedly at a particular point of the scene. These effects are essentially characterized by deformations and displacements of parts of the environment. It is suggested that the phenomenon responsible for them is the loss of size and position constancy, respectively. Experimental evidence indirectly validates this hypothesis, and a program of studies is now under way to further corroborate it.