Abstract
Previous studies have shown that tool use often modifies one's peripersonal space – i.e. the space directly surrounding our body. Given our profound experience with manipulable objects (e.g. a toothbrush, a comb or a teapot) in the present study we hypothesized that the observation of pictures representing manipulable objects would result in a remapping of peripersonal space as well. Subjects were required to report the location of vibrotactile stimuli delivered to the right hand, while ignoring visual distractors superimposed on pictures representing everyday objects. Pictures could represent objects that were of high manipulability (e.g. a cell phone), medium manipulability (e.g. a soap dispenser) and low manipulability (e.g. a computer screen). In the first experiment, when subjects attended to the action associated with the objects, a strong cross-modal congruency effect (CCE) was observed for pictures representing medium and high manipulability objects, reflected in faster reaction times if the vibrotactile stimulus and the visual distractor were in the same location, whereas no CCE was observed for low manipulability objects. This finding was replicated in a second experiment in which subjects attended to the visual properties of the objects. These findings suggest that the observation of manipulable objects facilitates cross-modal integration in peripersonal space.
Highlights
From morning to night we use many objects that extend our bodily capabilities and that make our life much easier
The analysis of the inverse efficiency (IE) during the cross-modal congruency task revealed a main effect of congruency, F(1,15) = 13.2, p,.005, g2 = .47, reflecting faster responses for congruent (876 ms, SE = 90 ms) compared to incongruent trials (922 ms, SE = 86 ms) and thereby confirming that the basic congruency manipulation was successful
A significant interaction was observed between congruency and object type, F(2,30) = 4.0, p,.05, g2 = .21, reflecting that the congruency effect (CCE) differed between different stimulus categories
Summary
From morning to night we use many objects that extend our bodily capabilities and that make our life much easier. In humans comparable effects of tool use have been established, by investigating the interference effect of distractor lights presented near the end of the tool on the discrimination of tactile stimuli applied to the hand [4,5,6,7,8] In this task subjects respond faster when the spatial position of the distractor light is congruent compared to incongruent with the felt vibration (i.e. up or down), which is known as the cross-modal congruency effect (CCE). The finding that the crossmodal congruency effect extends towards the end of the tool suggests that tool use extends one’s peripersonal space [4]
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