Perceptual aftereffects of sustained fixation and oculomotor changes

Several conditions induce correlated perceptual and oculomotor changes. Often the perceptual aftereffects are treated as a result of the oculomotor ones. Some results are reported that cast doubt on this interpretation of the aftereffects of sustained convergence. First, the inspection distance that induces no aftereffect is nearer than the vergence resting position. Second, there are at least two situations in which the expected correlation between perceptual and oculomotor changes breaks down: (1) inspection of a near stimulus below eye level tends to induce a subsequent overestimation of the distance of a test stimulus that is accompanied by an exophoric shift instead of the expected exophoric one, and (2) closing one's eyes for some minutes induces an exophoric shift without a perceptual aftereffect. These results suggest that at least in some situations perceptual and oculomotor changes may be functionally independent.