Task demands shift motor learning from adaptation to feedback control in an unconstrained bimanual task

Abstract

Bimanual actions are common in daily life, yet how task demands shape reliance on learning and control mechanisms remains largely unknown. We examined this in 73 participants who lifted a plate in virtual reality while we distorted visual motion of their right hand. During right-hand-only lifting, aftereffects were present but incomplete. Bimanual lifting with the same right-hand perturbation shifted learning further from adaptation toward feedback control: participants developed compensatory hand adjustments and showed smaller aftereffects. Relaxing precision demands improved success but neither restored aftereffects nor reduced compensation. Removing interlimb conflict by perturbing both hands did not improve success but eased compensatory adjustments and restored plate aftereffects to unimanual levels. Success rate during learning did not correlate with aftereffects, but faster movement speed did. This demonstrates that precision demands and interlimb conflict independently shift learning strategy in bimanual contexts.