EFFECTS OF CUEING AND OF THE DIRECTION OF SCANNING ON THE TACTILE LINE BISECTION OF NORMAL ADULTS

The effect of two variables, cueing one side of the line and imposing a fixed direction of scanning, were studied in the tactile line bisect ion of normal adults. The results of Experiment 1 showed that when one side of the line was cued, errors tended to be pulled toward that sid e. However, the deviations did not differ from zero. Experiment 2 exam ined the effect of imposing a fixed direction of tactile scanning (lef t to right only, or right to left only). The results revealed overshoo ting errors, i.e., deviations in the direction of the extremity of the stimulus opposite to the starting point of scanning. These deviations differed significantly from zero. Finally, in all control groups (two cues or no cue in Experiment 1, scanning in both directions in Experi ment 2), each hand tended to deviate in the direction of the contralat eral space. These results were tentatively explained in terms of some specific characteristics of the tactile modality: the fact that it is a proximo-receptor and the role of motor processes in the tactile mode of information processing.