Line bisection performances of 650 normal children

When bisecting lines, an important number of brain damaged patients tend to place their bisection marks in the hemispace ipsilateral to their lesion. Biases have also been reported in normal adults. In vertical bisection both patients and normal subjects present with upward shifts, although a downwa rd displacement may occur eventually. Surprisingly, little is known on line bisection (LB) in normal or brain damaged children. A total of 650 subject s, aged 7-12 years, performed a horizontal and vertical LB task with their preferred hand. Asymmetry indices (AIs) were used to measure directional bi ns. Unsigned Als served to evaluate accuracy and mastery of the LB skill. I n vertical bisection a general and significant upward bias was found, where as in horizontal bisection subject (gender. handedness, utilized hand, age) and stimulus variables (orientation, length, position) yielded significant ly different AIs. Although with increasing age significantly increasing acc uracy was observed, none of the participating children mastered LB to mathe matical precision. Differences in IQ-level and attention lest score did not yield significantly different AIs. Impact from reading proficiency could n ot be demonstrated. It is suggested that stimulus length effect results are compatible with the Halligan and Marshall [Halligan, P., and Marshall, J. Toward a principled explanation of unilateral neglect. Cognitive Neuropsych ology, 1994, 11, 167-206] model of hemispatial neglect. Moreover, data may support the hypothesis of greater hemispheric specialization of visuo-spati al skills in boys than in girls. (C) 2000 Elsevier Science Ltd. All rights reserved.