Partial adaptation to surface movement during hand reaching.

Humans can effectively adapt to changes in the environment to maintain adequate motor performance in a vast range of situations. However, residual errors tend to persist when strong a priori assumptions about the statistical regularities of the environment are violated. In our study, we challenged the expectation that inanimate objects are usually at rest. To this end, we used a robotic interface to move a plate over which participants slid their finger while reaching toward a target. We found limited evidence of adaptation after prolonged exposure to this perturbation, and only when visual feedback about hand position was provided. Although participants were aware of the motion of the contact surface, explicit knowledge about its direction was limited. Our results provide important insights into the limits of adaptation to motion perturbation in the somatosensory system, which can inform the design of technology applications such as haptic interfaces and collaborative robots.NEW & NOTEWORTHY Humans can adapt to environmental changes in a vast range of situations, but systematic errors remain when strong a priori assumptions are violated. We tested the assumption that inanimate objects are stationary by moving a plate under participants' fingers while they reach a target. We found limited adaptation, mainly when visual feedback of hand position was provided. Despite awareness of surface motion, directional knowledge was poor. These findings inform the design of haptic and robotic interfaces.