What are the spatial limits of tactile perception?

Intuitively, the human sense of touch is body-centric; that is, it is concerned with the detection and localization of objects contacting the body surface. In this talk, I will present data that questions this intuition. Specifically, I will discuss our recent research that has demonstrated that humans can use hand-held tools as sensory extensions of their body. I will first discuss several behavioural studies that applied classic body-centred localization paradigms to localizing touch on a tool. These studies found that human participants can do this very accurately. This is even the case when the tool is six-meters long and when complex sensorimotor transformations are necessary to do the task. I will then present EEG evidence suggesting that the human nervous system re-uses low-level neural processes for localizing touch on the body to localize touch on a tool. These neural signals contain fine-grained information about the precise location of touch on a tool. In all, these findings argue that a tool becomes an integrated part of the somatosensory system when wielded, readily extending tactile perception well beyond the spatial limits of the body.