Presentation at ASSC 15

An abstract based on our recent pilot study with the Enactive Torch has been accepted as a presentation at this year’s annual conference of the Association for the Scientific Study of Consciousness (ASSC), to be held in Kyoto, Japan, on June 9-12.

Distal perception via use of distal-to-tactile sensory substitution interface does not lead to extension of body image

Tom Froese, Marek McGann, and Anil K. Seth

It is well known that bodily transformations are entailed by practical tool-use, such as changes in body schema and body image after pointing with sticks or manipulating with rakes (see Maravita and Iriki 2004). What remains unclear is which aspects of tool-use cause the transformations. Since no effects are found in control tasks with laser pointers, the changes appear to be related to reachability (Longo and Lourenco 2006).

But is reachability important because elongated tools enable subjects to perceive at a distance, like a blind person using a cane? Or because such tools enable subjects to act at a distance, like a subject using a rake to retrieve an object? Comparisons between elongated tools and laser pointers cannot resolve this question (elongated tools enable both factors simultaneously, while laser pointers enable neither of them).

We used a custom-built hand-held sensory substitution device, the Enactive Torch (Froese and Spiers 2007), to investigate this issue. Subjects trained in using this device, which converts distance measurements into tactile vibrations in the hand, readily report the perceptual experience of things ‘out there’. However, in contrast to the case of using elongated tools, this novel perception at a distance is not accompanied by a change in the possibility for directly acting at a distance. We tested 20 participants but found no evidence of a transformation in their perceived arm length. This suggests that it is the change in the potential for action, not perception, which is the decisive factor for transformations of the body image.