Human force reproduction error depends upon force level

For optimal haptic tele-manipulation system design, it is important to understand the accuracy and limitations of human force perception. Previous research demonstrated that humans generate higher forces when asked to reproduce an externally applied force; these studies proposed that the nervous system attenuates feedback from self-generated forces. The goal of this study was to determine how accurately subjects reproduce self-generated forces with the same hand over a broad range of force levels. Subjects (n=10, all right handed) had to generate an onscreen target force with visual support and subsequently reproduce the same force without visual support with their right hand against a static handle equipped with a force sensor. Six force levels (10 to 160N) were each presented randomly for eight repetitions. Subjects generated too high forces for lower force levels (≤40N) and too low forces for higher force levels (≥ 130N). Our results support force-dependent sensory integration and demonstrate that attenuated feedback of self-generated forces is not the sole factor in force reproduction errors.