Abstract
Previous work by our group had participants make haptic-based manual estimations (with the right hand) of the size of objects placed on the forearm and palm of their left limb and subsequently reach to grasp the object. Haptic judgments in the palm, but not the forearm, condition elicited an adherence to the psychophysical principles of Weber’s law. In reconciling this finding, we proposed that the requirement to grasp the object influenced the nature of the haptic information supporting response output. The present study was purpose-designed to address that proposal and had participants (N=14) make haptic-based manual estimations about the width of objects positioned on the palm and forearm of their left limb in tasks wherein manual estimations were followed (i.e., tactile feedback: TF) or not followed (i.e., no tactile feedback: NTF) by a grasping response. As well, we included a task wherein estimations were completed by adjusting the width of a line appearing on a computer monitor (i.e., line drawing: LD). In line with our previous work, the TF task showed that haptic judgments in the palm but not the forearm condition adhered to Weber’s law. In contrast, NTF and LD tasks showed a reliable adherence to Weber’s law across palm and forearm conditions. Based on these results, we propose that the availability of terminal tactile feedback in a lower receptor region (i.e., the forearm) alters the haptic-based scaling of stimulus intensity from relative to absolute metrics.Acknowledgments: NSERC