A Sensitive Period for Automaticity Rather than Ability: Automatic Visuospatial Coding of Touch Requires Visual Experience in Early Life

Early visual experience can profoundly shape tactile perception. Sighted and late blind but not congenitally blind humans automatically link touch to a visuospatial reference frame-evidenced by a tendency to assign tactile stimuli to the wrong hand when the hands are crossed. Here, we tested for a sensitive period during which visual experience irrevocably shapes the automaticity of visuospatial coding of touch. To this aim, tactile spatiotemporal perception was measured in individuals who had been temporarily blind due to bilateral dense cataracts that were either congenital or developed in childhood. Participants reported the location of the first of two successive tactile stimuli-one on each hand-resting their arms in a crossed or uncrossed position. In Experiment 1, only tactile stimulus pairs were presented (unimodal context). In Experiment 2, pairs of tactile stimuli were interleaved with tactile-auditory and auditory pairs (crossmodal context). In the unimodal context, individuals with restored congenital cataracts-reminiscent of those with congenital blindness-did not exhibit the typical impairment with crossed hands, confirming irrevocable effects of early vision on tactile perception. In stark contrast, in the crossmodal context, hand crossing markedly impaired their tactile judgments. Here, individuals with restored congenital cataracts performed similarly to typically-sighted individuals. Thus, the genuine ability to code touch visuospatially did not depend on early vision. Participants with restored childhood-onset cataracts and typically-sighted participants showed comparable crossing effects in both contexts. In sum, the present study reveals that the automaticity rather than the ability to code touch visuospatially requires early visual experience.