Sensory Substitution and Intentionality

by Joshua Siegle

Joshua Siegle

In the study of the brain, an organism's knowledge of external objects is often accounted for by the presence of neural representations that track those objects. Unfortunately, as long as these representations are treated as symbols in a "neural code" to be manipulated by the brain, neuroscience cannot offer an adequate explanation of how perceptual states can be intentional-that is, directed at elements of the environment. Sensory substitution offers a means to study the neural mechanisms of intentionality, a philosophical concept that has not received ample attention from neuroscience, given the instrumental role it plays in perception. In this study, information about the ambient light was transmitted through the skin of blindfolded human subjects in order to study the rise of a novel intentional relation. Not only were subjects able to use this information to successfully orient their behavior toward a light in their environment, the precision of their judgments approached that of sighted subjects. Changes in the phenomenal experience of a distal object were correlated with changes in ability, suggesting that subjects were learning a perceptual, rather than cognitive, skill. Furthermore, once the skill was acquired, it transferred to new limbs and body positions. This indicates that the skill is not limited to a single sensorimotor system. The findings support a theory of perception based on invariance, one which may be better able to accommodate the existence of intentionality than the prevailing views in contemporary neuroscience. A distinguishing feature of the invariance view is that it explains how we can (and why we must) perceive external objects, rather than internal representations.