Adaptation to optically reduced size.

Abstract

Previous investigators have reported some difficulty in obtaining evidence for adaptation to optically reduced size. A study is reported in which a ballistic target-pointing task was used to examine such adaptation. In the first experiment size was reduced either by means of negative spherical lenses, or cylindrical lenses which reduced image size in only one dimension. Both lens types produced a negative aftereffect of adaptation, which increased as a function of lens strength. There was also a tendency for cylindrical lenses to give larger aftereffects. In a second experiment, in which a modified adaptation procedure was used, adaptation to cylindrical distortion was found to be significantly greater than adaptation to equivalent spherical distortion. These data are interpreted with respect to the relative amounts of distance distortion induced by viewing through the different lens types. The third experiment employed a cylindrical lens and a mental rotation procedure to determine whether adaptation in the first two experiments may have been visual or visuomotor in nature. Results indicated that adaptation was not purely visual. It is concluded that it is possible to demonstrate adaptation to size distortion by using an appropriate procedure.