Role of feedback in the accuracy of perceived direction of motion-in-depth and control of interceptive action

We quantified the accuracy of the perception of the absolute direction of motion-in-depth (MID) of a simulated approaching object using a perceptual task and compared those data with the accuracy of estimating the passing distance measured by means of a simulated catching task. For the simulated catching task, movements of the index finger and thumb of the observer's hand were tracked as participants tried to "catch" the simulated approaching object. A sensation of MID was created by providing monocular and/or binocular retinal image information. Visual stimuli were identical for perceptual and simulated catching tasks. We confirm previous reports that in the perceptual task, observers judged the object to pass wider of the head than indicated by the visual information provided. Although accuracy improved when auditory feedback was added to the perceptual (button pressing) task, consistent overestimates were still recorded. For the no-feedback simulated catching task, observers consistently overreached, i.e., the hand was further away from the midline than the simulated object at the time of hand closure. When auditory feedback was added to the simulated catching task successful catching was achieved. The relative accuracy in binocular and monocular conditions for individual observers could be partially explained by individual differences in sensitivity to unidirectional changes in angular size and changes in relative disparity. We conclude that catching an approaching ball requires that errors in the perceived direction of MID are corrected by feedback-driven learning in the motor system, and that this learning is more easily achieved for the catching action than for button pressing.