Distortions in definite distance and shape perception as measured by reaching without and with haptic feedback

Psychophysical studies reveal distortions in perception of distance and sha pe. Are reaches calibrated to eliminate distortions? Participants reached t o the front side. or back of a target sphere. In Experiment 1, feedforward reaches yielded distortions and outward drift. In Experiment 2, haptic feed back corrected distortions and instability. In Experiment 3, feedforward ca ches with only haptic experience of targets replicated the shape distortion s but drifted inward. This showed that outward drift in Experiment 1 was vi sually driven. In Experiment 4, visually guided reaches were accurate when participants used binocular vision but when they used monocular vision, rea ches were distorted. Haptic feedback corrected inaccuracy and instability o f distance but did not correct monocular shape distortions. Dynamic binocul ar vision is representative and accurate and merits further study.