The ontogeny of spatial perception in sighted and blind infants

Abstract

Congenitally blind infants develop in a perceptual environment which not only lacks visual input but is also deprived of the influences of vision on the intact senses such as in crossmodal calibration and the mapping of the senses to external spatial coordinates. Comparing early spatial representations in blind and sighted infants, we elicited manual orienting responses to auditory and tactile stimuli presented on infants’ hands, manipulating arm posture to examine the frames of reference used for localisation. The sighted infants oriented to auditory cues in audiotactile presentations, and used an external spatial code when locating touches (they showed a crossed hands deficit [6]). The blind infants oriented to tactile cues in audiotactile presentations and used an anatomical spatial code for locating touches, notably showing improved tactile localisation than the sighted participants in the crossed hands condition. Both the sighted and the blind infants demonstrated improved localisation when auditory stimuli were presented at the same time and on the same hand as tactile stimuli, but the blind infants showed a weaker multisensory gain. The blind infants’ responses to touches at the expense of auditory cues indicates an impairment of auditory localisation, leading to a spatial bias to anatomical rather than external coordinates. The finding of multisensory gain across blind and sighted infants demonstrates multisensory integration. This shows that spatial localisation can be enhanced in blind infants by providing spatially congruent stimulation across audition and touch, a finding which bears important implications for approaches to early intervention.