Evidence for haptic memory

The purpose of these experiments was to investigate the minimum duration of haptic memory representations. The term haptic memory can be defined as the ability to retain impressions of haptically acquired information after the original stimulus is absent. Participants repeatedly picked up objects of various masses. The time interval between the final practice lift of each object and a test lift was manipulated. In the 0 second delay condition, there was no delay between the release of the object after the final practice lift and the test lift. In the 2 and 10 second delay conditions there was a 2 or 10 second delay, respectively, between the release of the object after the last practice lift, and the test lift. Greater peak grip force was produced for the first lift compared to the subsequent practice lifts. In the 0 second delay condition, the peak grip force used in the test lift was similar to the last practice lift. As the delay increased to 10 seconds, the peak grip forces used were similar to that of the first lift. Even after a 2 second delay the peak grip force was greater than that of the last practice lift. Peak torque also followed these same patterns. The present results suggest that the haptic representation of object mass is short-lived (< 2 s) and has a duration and decay similar to visual iconic memory.