Movement and illumination factors in adaptation to prismatic viewing

While wearing laterally displacing prisms, Ss were required to align a spot of light to the phenomenal straightahead. These measurements were obtained at the beginning and at the end of an exposure to prismatic displacement. In addition, Ss either actively controlled movement of the spot of light, or movement was manipulated by E under the direction of the S. Aftereffects were determined by having S position the spot of light with normal vision at the beginning of the experiment and after each measurement obtained under prism viewing. Ss in the darkened room condition who were required to align the spot of light actively showed a significant aftereffect in the direction of prismatic displacement both at the beginning and at the end of the exposure period. No difference in the degree of adaptation was found between those measurements at the beginning and at the end of the exposure period. No significant aftereffects were found when the room was illuminated during prism exposure or when E controlled movement of the light source.