Tactual-kinesthetic matching of horizontal extents by the long-term blind: absence or reversal of normal left-side underestimation.

Ten adults, who were blind from infancy or childhood, laterally slid a horizontal rod within a short length of pipe located at the body midline, until the rod extremities were tactually-kinesthetically judged to be equidistant from the ends of the pipe. Whereas sighted subjects normally set the left extremity of the rod closer to the midline than the right irrespective of arm posture, crossed or uncrossed, blind subjects, especially those blind from birth showed trends in the opposite direction. The role of vision is discussed with respect to the development and expression of asymmetries relating to the coding of extracorporeal space.