Role of Proprioceptive and Tactile Feedback in Small Size Discrimination

The human hand relies on information from surrounding environment to distinguish objects based on qualities like size, texture, weight, and compliance. The size of an object can be determined from tactile feedback, proprioception, and visual feedback. This experiment aims to determine the accuracy of size discrimination in physical and virtual objects using proprioceptive and tactile feedback. Using both senses will help determine how much proprioceptive and tactile feedback plays a part in discriminating small size variations and whether replacing a missing sensation will increase the subject's accuracy. Ultimately, determining the specific contributions of tactile and proprioceptive feedback mechanisms during object manipulation is important in order to give prosthetic hand users the ability of stereognosis among other manipulation tasks. Two different experiments using physical and virtual objects were required to discover the roles of tactile and proprioceptive feedback. Subjects were asked to compare the size of one block to a previous object. The blocks increased in size by two millimeter increments and were randomized in order to determine whether subjects could correctly identify if a box was smaller, larger, or the same size as the previous box. In the proprioceptive experiment subjects had two sub-sets of experiments each with a different non-tactile cue. The experiment demonstrated that subjects performed better with physical objects compared to virtual objects. This suggests that size discrimination is possible in the absence of tactile feedback, but tactile input is necessary for accuracy in small size discrimination.