Shape discrimination in active touch: Effects of exploratory direction and their exploitation

The active control of exploratory movements is an integral part of active touch. In two experiments we investigated (and manipulated) the relationship between the haptic discrimination of small bumps and the direction of exploratory movements relative to the body. Shape discrimination performance systematically varied with the direction of stimulus exploration. Further, if they were rewarded for good perceptual performance and had the choice, participants displayed clear strategic preferences for certain exploratory directions. Chosen directions, at least on average, were accompanied by low discrimination thresholds. Overall, the findings emphasize the necessity to focus at the explorator's active contribution to haptic perception, and provide the first hints that exploratory behavior might be exploited to optimize haptic perception.