Sensory Substitution: Unfulfilled Promises and Fundamental Limitations

Many of the most attention-grabbing claims concerning the uptake of sensory substitution devices in the last 50 years have, noticeably, not come to pass. I highlight a number of the fundamental limitations (some acknowledged, others not) that may have prevented the development and uptake of these devices amongst individuals suffering from sensory loss. First and foremost, it may simply be impossible to fully substitute for the loss of vision (the sense most substituted for) given the imbalance in neural cortical resources given to processing information in the various senses. Second, the inability to substitute for the hedonic attributes of a given modality constitutes an important, if currently under-acknowledged, problem. Most researchers tend to focus their efforts on the substitution of the sensory-discriminative (primarily spatial) aspects of stimulation instead. Third, I highlight the technological limitations associated with providing useful substitution devices for those who have lost their sense of taste or smell, senses which, theoretically, should be far easier to substitute for. Another factor that may have limited the uptake of these devices—aesthetic concerns about the appearance of users wearing them—is, I believe, likely to disappear, as a range of other augmented-perception technologies become more widely accepted.