BISECTION AND PERCEPTION OF HORIZONTAL LINES IN NORMAL-CHILDREN

Simple line bisection is a complex task in which both perceptual/atten tional factors and motor factors are involved. Using a judgment task o n prebisected lines it is possible to assess independently the role of perceptual/attentional factors. The judgment-bisection relationship w as investigated in 37 preschool children aged 4-5 and 70 school childr en aged 10-12. At bisection, a clear shift of the right hand with age from right to left bisections was observed, more pronounced in right- than in left-handers, and probably related to learned patterns. At jud gment, a slight but significant left side overestimation was observed. In right-handers, judgment was related to left-hand but not to right- hand bisection. It is concluded that motor (manual) factors strongly i nfluence visuo-motor bisection in normal children, and it is suggested that the judgment-bisection relationship has to be systematically inv estigated when bisection is used as a task informing on space percepti on or on direction of attention.