Right and Left Hand Skill in Left-Handers: Distribution, Learning, and Relation to Nonverbal Intelligence

Publisher Website
Google Scholar
Abstract
The relation of hand skill to nonverbal intelligence (spatial reasoning) tested by Cattle's Culture Fair Intelligence Test was studied in left-handed subjects. Hand skill was assessed by the peg moving test, which revealed that some of the left-handers (Geschwind scores and self-reports) were ambidexters. The distribution for right hand skill fitted to Gaussian data better than that for left hand skill. The R-L difference between the hands in peg moving times could also be described by normal distributions in the total sample, ambidexters, and left-handers. The right and left hands of ambidexters were as fast as the left-handers. In left-handers, the right hand was significantly slower than the left hand. In males, right-hand skill fitted to Gaussian data better than left-hand skill. In males and females, right and left-hand skill fitted to Gaussian data. Left-hand skill fitted to Gaussian data better in females than males. The difference between right- and left-hand peg-moving times was found to be larger in females than males. There was no significant difference between the right- and left-hand peg moving times of the male and female left-handers. The mean peg moving times for the right and left hands linearly decreased at each successive trial (N = 10). This motor learning was found to be better in left-handers with high IQs than those with low IQs. The right hand of left-handers with high IQs was faster than that with low IQs. The motor learning of the left hand was not different in left-hnaders with high and low IQs. The regression line for ambidexters exhibited less learning than that for left-handers. It was suggested that right hand skill is associated with nonverbal intelligence in left-handers, indicating the importance of left hemispheric processing in this kind of cognitive performance.