Differential laterality of hand function in right-handed and left-handed boys.

This study was designed to investigate differences in the degree of manual lateralization between right-handed and left-handed normal boys. Sixty-three 5, 7, and 9 year olds were tested on the Minnesota Rate of Manipulation Test (displacing subtest and turning subtest), the Finger Tapping Test, the Purdue Pegboard (placing subtest and assembly subtest), and the Southern California Motor Accuracy Test--Revised. Significant differences between right- and left-handed subjects were obtained on two of the six measures, and a third measure approached significance, with less lateralization among the left handers than among the right handers. Subsequent analyses indicated that differences in lateralization were significant or near-significant in the 5 and 7 year olds. By 9 years of age, right- and left-handed subjects no longer differed in the degree of laterality. Differences in degree of laterality, or the lack of such differences, between young right- and left-handed boys might be a function of the nature of the fine motor task or a function of the child's previous experience with the task.