Abstract
The recruitment of bimodal visual-tactile neurons may explain the enhanced processing of visual stimuli near the hand. The present study investigated whether or not the ‘hand-related enhancement effect’ would extend to a novel tool after training. Participants (N=32) were asked to press a button as rapidly as possible with their right hand when they detected a target projected onto the surface of their left hand, a fake hand, or a tool. After the baseline session, all subjects were tested when holding the fake hand and tool with their left hand. The stimuli were presented on the hairy surface of the fake hand and the top surface of the tool. 16 subjects were then trained to use the fake hand (FH-group) and 16 to use the tool (Tool-group) to move a ball around complex path with their left hand. After training, all subjects were again tested when holding the tool and the fake hand. Finally, three baseline conditions were re-tested. We found that the participants initially responded faster to stimuli projected onto their real hand (307ms) than to stimuli presented on fake hand (318ms) or the tool (331ms), p[[lt]].004. After training, participants in the FH-group now responded faster to the target lights projected on the fake hand than they did before training (p=.004). Similarly, participants in the Tool-group showed the same pattern with the tool (p[[lt]].000). Finally, the FH-group (but not the Tool-group) responded faster to targets on the hairy as opposed to the glabrous surface of the fake hand (p=.005), even when they were not holding the fake hand, whereas the Tool-group (but not the FH-group) responded faster to targets on the top of the tool compared to the bottom (p=.029). These findings suggest that an enhancement effect can be induced in tools and other inanimate objects with training.
This research was funded by a grant to MG from Natural Sciences and Engineering Research Council of Canada.