Proprioceptive Misestimation of Hand Speed

The accuracy with which the human proprioceptive system estimates hand speed is not well understood. To investigate this, we designed an experiment using hobby-grade mechatronics parts and integrated it as a laboratory exercise in a large remote laboratory course. In a simple joint position reproduction task, participants (N = 191) grasped a servomotor-driven shaft with one hand as it followed a randomized trajectory composed of sinusoidal submovements. They simultaneously attempted to reproduce the movement by turning the shaft of a potentiometer with the other hand. Focusing on the first movement of the trajectory, we found that participants consistently overestimated the speed of the slowest rotations by ~45% and underestimated the speed of the fastest rotations also by ~30%. Speed estimation errors were near zero for trajectories with peak velocities ~63 deg/s. Participants' movements also overshot slow trajectories and undershot fast trajectories. We show that these trajectory errors can be explained by a model in which the proprioceptive system integrates velocity misestimates to infer position.