Introduction

The concept of sensory compensation was proposed by the philosopher Diderot, in “Lettre sure les Aveugles,” published in 1749. Sensory compensation refers to improvement in the remaining senses after the loss of one sensory system in order to counteract the lost capabilities. Along these lines, William James in 1890 proposed that loss of vision should promote the learning of extraordinary perceptual skills in the intact modalities. However, the empirical literature on this issue is inconclusive; both superior and inferior performance have been reported for blind individuals in comparison with sighted individuals and for deaf persons in comparison with normal-hearing individuals (for reviews, see Röder & Neville, 2003; Röder & Rösler, 2001). Reasons for the contradictory results on testing most likely originate in the characteristics of the participants recruited for the studies (e.g., etiology, degree, duration and age at onset of sensory impairment, age at testing) and the tasks used (e.g., different tasks were used for the experimental group and the control group, instructions were not always adequate for blind or deaf participants) (for detailed discussions of these issues, see Millar, 1982; Röder & Neville, 2003; Thinus-Blanc & Gaunet, 1997).

This chapter reviews findings in blind and deaf individuals for different functional domains, including perceptual, language, and spatial functions. To understand what the underlying neural mechanisms of cross-modal compensation are, some relevant findings from animal research are reported and the meaning of the term neuroplasiticity is discussed. The focus is on the visual deprivation model, but some parallel findings in the deaf are reported as well.