It is only when the displacement of the retinal image differs from the displacement predicted on the basis of the efference copy, i.e., when the latter fails to “cancel out” the former, that subjects experience a change of some sort in the perceived scene (see Figure 1). The relevant upshot is that VDC has an essential motoric component: the apparent stability of an object’s eye-relative position in the world depends on the perceiver’s ability to integrate incoming retinal signals with extraretinal information concerning the magnitude and direction of impending eye movements.