We report several experiments directed at the ability of humans to perceive the spatial orientation of occluded objects, to position an occluded limb relative to targets or directions in the environment, and to match the spatial orientations of occluded contralateral limbs. Results suggest that each of these abilities is lied to the inertial eigenvectors of each object or limb, which correspond to the object's or limb's principal axes of rotational inertia. Discussion focuses on the dynamic nature of proprioception, the importance of physical invariants for perception, and the relation of invariants to hypothesized frames of reference for proprioception and motor control. It is suggested that the detection of invariants revealed through movement is a major mechanism in kinesthetic perception involving intact limbs, neuropathic or anesthetized limbs, prosthetic devices, and hand-held tools and implements. The inertia tensor is identified as one such invariant.
Christopher C. Pagano is with Clemson University, Clemson, SC, and the Center for the Ecological Study of Perception and Action, University of Connecticut, Storrs, CT. Michael T. Turvey is with the Center for the Ecological Study of Perception and Action. University of Connecticut, and Haskins Laboratories, New Haven, CT. Direct correspondence to Christopher C. Pagano, Clemson University. Department of Psychology. 418 Bracken Hall, Clemson, SC 29634-1511. email@example.com
Editor’s Note:At the 21st Annual Meeting of the American Society of Biomechanics, held September 1997 at Clemson University, I had the distinct privilege of introducting Michael T. Turvey, who had been invited by the program committee to present a key-note lecture. Dr. Turvey’s lecture was a thought-provoking integration of biomechanics with motor control that included modeling-based predictions and experimentally derived validations of those predictions. I was pleased when Drs. Turvey and pagano agreed to contribute this invited paper to the Journal of Applied Biomechanics. —M.G.)