ACCURACY AND ADAPTATION OF REACHING AND POINTING IN PITCHED VISUAL ENVIRONMENTS

Visually perceived eye level (VPEL) and the ability of subjects to rea ch with an unseen limb to targets placed at VPEL were measured in a st atically pitched visual surround (pitchroom). VPEL was shifted upward and downward by upward and downward room pitch, respectively. Accuracy in reaching to VPEL represented a compromise between VPEL and actual eye level. This indicates that VPEL shifts reflect in part a change in perceived location of objects. When subjects were provided with termi nal visual feedback about their reaching, accuracy improved rapidly. S ubsequent reaching, with the room vertical, revealed a negative aftere ffect (i.e., reaching errors that were opposite those made initially i n the pitched room). In a second study, pointing accuracy was assessed for targets located both at VPEL and at other positions. Errors were similar for targets whether located at VPEL or elsewhere. Additionally , pointing responses were restricted to a narrower range than that of the actual target locations. The small size of reaching and pointing e rrors in both studies suggests that factors other than a change in per ceived location are also involved in VPEL shifts.