Haptic Length Display Based on Cutaneous-Proprioceptive Integration

When a human recognizes length of an object while exploring it with an index finger, both proprioception and cutaneous sensation provide information for estimating the length of the object. We studied the contribution of cutaneous sensation and proprioception to the subjective estimation of object length, developing an apparatus for investigating the human cutaneous-proprioceptive integration using velocity dependency of cutaneous and proprioceptive length perception. We conducted four experiments. In experiment 1, 12 subjects estimated object length passively, using cutaneous sensation only via the index finger. In experiment 2, ten subjects estimated the distance if index finger traveled passively without cutaneous sensation. In experiment 3, subjects used both cutaneous and proprioceptive sensation to estimate the object length. The results showed that using both senses simultaneously improves length perception. In experiment 4, 17 subjects estimated object length moving the index finger passively but with the cutaneous sensation and proprioception differing in perceived length. The results showed that subjects relied on the greater sensation if proprioceptive and cutaneous sensations were discrepant.