Abstract EN:

Bowers and heilman (1980) observed that when righthanded adults were asked to locate, in the hapic modality, the midpoint of a horizontal line, both hands tended to deviate to the left of the true midpoint. This error, called "pseudoneglect" by reference to the rightward error of patients suffering from right posterior brain lesions, was also observed in vision and has been explained by hemispheric activation theories. Because bisection is spatial in nature, it would activate the right hemisphere and would therefore induce a left lateral shift of attention. In our research on bisection in the haptic modality of normal blindfolded and totally blind adults, we first replicated bowers and heilman's results (sampaio & philip, 1991). But further studies failed to confirm the existence of pseudoneglect. Actually, each hand tended to deviate in the contralateral space. In addition, when the direction of exploration of the line to be bisected was constrained (from left-to-right only, or from right-to-left), the responses were deviated in the direction of the arm movement. Finally, attentional priming of one end of the stimulus tended to deviate the subjective midpoint in the direction of the lateral cue. These results are discussed in relation to hemispheric activation theories and to the hypothesis assuming changes in the egocentric reference frame.