Manual skill, hand skill asymmetry, and cognitive performances in young children.

A total of 1022 children aged 3 to 6 years were examined in their preschools and 27% of them were followed up for 2 years. A computerised version of the peg-moving task was used repeatedly to assess hand skill of the dominant and the nondominant hand. Cognitive performance was repeatedly evaluated by tasks involving speech, vocabulary, phonological memory, and visual-spatial skills. Results showed that: (i) age, sex, and handedness effects on hand skill asymmetry generally confirmed previous reports, especially by Annett (2002); (ii) visual-spatial and vocabulary tasks were significantly related to hand skill but speech and phonological memory tasks were not, and the role of the dominant and nondominant hand were similar; (iii) overall, manual laterality indexes were only weakly associated to some cognitive abilities; (iv) early manual skill was more strongly associated to cognitive tasks than later manual skill. These results fit the assumption of a significant role of early manual behaviour in aspects of cognitive development not relying exclusively on phonology, and raise questions about cognitive development and rehabilitation of children with early occurring manual deficiencies.