Does tool use extend peripersonal space? A review and re-analysis

Holmes, N. P. (2012) Does tool use extend peripersonal space? A review and re-analysis. Experimental Brain Research, 218 (2). pp. 273-282. ISSN 1432-1106 doi: 10.1007/s00221-012-3042-7

Abstract/Summary

The fascinating idea that tools become extensions of our body appears in artistic, literary, philosophical, and scientific works alike. In the last fifteen years, this idea has been re-framed into several related hypotheses, one of which states that tool use extends the neural representation of the multisensory space immediately surrounding the hands (variously termed peripersonal space, peri-hand space, peri-cutaneous space, action space, or near space). This and related hypotheses have been tested extensively in the cognitive neurosciences, with evidence from molecular, neurophysiological, neuroimaging, neuropsychological, and behavioural fields. Here, I briefly review the evidence for and against the hypothesis that tool use extends a neural representation of the space surrounding the hand, concentrating on neurophysiological, neuropsychological, and behavioural evidence. I then provide a re-analysis of data from six published and one unpublished experiments using the crossmodal congruency task to test this hypothesis. While the re-analysis broadly confirms the previously-reported finding that tool use does not literally extend peripersonal space, the overall effect-sizes are small and statistical power is low. I conclude by questioning whether the crossmodal congruency task can indeed be used to test the hypothesis that tool use modifies peripersonal space.