BIRTH-WEIGHT AND HANDEDNESS IN BOYS AND GIRLS

The association between selected demographic variables and birth weigh t on the one hand and a composite hand preference score based on seven hand tasks (each performed twice) on the other was investigated in a sample of 1387 male and female schoolchildren aged 5 to 10 years old. In multiple regression models left-handedness was significantly more c ommon among boys and among children of better educated mothers and ten ded to decrease with age. No association was found with respect to urb an or rural residence or birth order. Increased birth weight was assoc iated with right-handedness in boys but with left-handedness in girls, and the birth weight by sex interaction term was statistically signif icant (p = 0.037). The demographic associations in the present study a re compatible with those reported previously. The different associatio ns of birth weight with hand preference in boys and girls indicate tha t the prenatal hormonal factors that affect brain lateralization and h andedness are qualitatively or quantitatively different in the two sex es and may be differentially associated with birth weight.