Sensory Substitution and Perceptual Emergence

Sensory substitution devices (SSDs) can be thought of as sensory prosthetics — as devices by which information normally represented by one perceptual modality is instead represented by an alternative, non-canonical channel involving a second perceptual modality. Given that sensory modalities ordinarily represent a very wide range of properties/events, it is no trivial matter to ensure that such prosthetic devices will capture the representational scope of the systems they aim to replace. Designers of such devices have often hoped to solve this challenge by building SSDs that succeed in representing the form(s) of basic energy normally represented by the impaired modality they are intended to replace, and then adding computational power to code up whatever can be derived from the basic energy. Thus, for example, the thought is that if we could build a device that represents in some alternative way the distal distribution of light intensity — the basic form of energy to which visual receptors are normally responsive — our device could, in principle, represent everything vision can represent: color, shape, form, motion, and so on. Unfortunately, I will argue, this attractively simple idea fails. For there appear to be features represented by our sensory modalities that are “perceptually emergent” — i.e., features whose exemplification is not fixed by the representation of the distribution of (the relevant forms of) basic energy. Hence, a SSD whose basic representational vocabulary is limited to the distribution of such basic energy will leave things out. None of this shows that SSDs will inevitably fail to represent what sensory modalities normally represent. It does suggest, however, that if we want them to represent what sensory modalities normally represent, then we will have to do more than preserve the representation of basic energy to which the substituted modalities are sensitive. ∗Department of Philosophy, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0119, [email protected]