Manual behavior, lateralization of manual skills and cognitive performance of preschool children.

Direction and degree of manual specialization (functional asymmetry between the hands) on a pegboard task, and fine motor ability (total number of pegs inserted) of both hands were correlated with verbal and visuospatial performances for 47 preschool children. No significant differences were found between right-, and left-, and mixed-handers even though the best motor skills were shown by the 6 mixed-handed subjects, who also had the highest scores on cognitive tasks. Verbal and visuospatial performances were not correlated with degree or direction of manual specialization. They were instead correlated with the level of motor ability of both hands. Motor maturation should be viewed, then, as a process that implies a richer motor performance of both hands and could be interpreted as a more specific diagnostic parameter than the traditional indices of handedness in cognitive fields.