The state of the art of sensory substitution.

As an introduction to the special issue of Multisensory Research on Sensory Substitution (SS) we would like to give an overview of the limits and promises of this growing field of research. It seems that a large part of the scientific community considers that sensory substitution does not work. Yet many research groups claim that it does, and are making advances and obtaining interesting results, many of which are described in this special issue, that support their case. Why is there this discrepancy? It is likely that the term ‘sensory substitution’ induces a narrowing of the field of research, linked to the original idea of fully restoring a lost sensory modality by artificially providing the information through another sense (e.g., Bach-y-Rita et al., 1969; see also Bach-y-Rita, 1972). However, such an ambitious claim has long been abandoned, and many researchers agree that SS is never going to be the way to achieve full recovery of the use of a lost sense. Many researchers do however agree that a restricted form of sensory substitution can be achieved. Thus, it is undeniably the case that many abilities of people with sensory loss can be significantly enhanced by the use of SS devices. To some extent, therefore, sensory substitution does work. Reflecting the fact that SS researchers have had to retract from their original ambitious aim, several alternative names for this cross-modal approach have been proposed such as ‘perceptual supplementation’ (Lenay et al., 2003) and ‘sensorimotor extension’ (Auvray and Myin, 2008). However, none has so far received universal acceptance. This may reflect the fact that, although SS