TACTILE AND VISUAL BISECTION TASKS BY SIGHTED AND BLIND-CHILDREN

Roeltgen and Roeltgen (1989) suggested that symmetrical patterns observed when young children bisect lines in a visuo-manual task could be due to callosal immaturity. To further investigate this hypothesis, the present study compared performances of sighted children in visuo-manual and tactile-kinesthetic bisection tasks. In addition two groups of visually handicapped children were tested with the tactile-kinesthetic bisection task. In the visuo-manual task, a symmetrical pattern was observed, confirming previous findings. However, in the tactile-kinesthetic task no symmetrical pattern was observed. Instead, sighted children bisected to the right of the midpoint with the left hand, totally blind children bisected to the left with both right and left hands, and no significant deviation was observed with partially blind children. The magnitude of the errors, irrespective of directionality, were not different between the three groups (sighted, totally blind, and partially blind children) in the tactile-kinesthetic task. These results suggest that past visual experience is not crucial to tactile length representation but affects tactile directional space representation. Furthermore, because visual performance differed from tactile performance, commisural immaturity seems an inadequate explanation of the observed results in children's line bisection tasks.