Hand preference: its provenance, development, and associations with intellectual ability at the age of 7.5 years.

The development of 199 children was studied at regular intervals from birth to 7.5 years. On each occasion hand preference was recorded. Their preferred hand was evident in 89.4% right and 85.7% left-handers by 4 years. Analyses on 242 children seen at birth and 7.5 years showed no associations between left-handedness and nine factors representing different aspects of "birth stress." For 12 of 15 aspects of ability at 7.5 years left-handed children had slightly higher scores than right-handers. Pathological factors do not seem to feature in the provenance or consequences of left-handedness in a normal healthy population.