THE PREVALENCE AND ORIGINS OF LEFT HAND PREFERENCE IN HIGH-RISK INFANTS, AND ITS IMPLICATIONS FOR INTELLECTUAL, MOTOR AND BEHAVIORAL PERFORMANCE AT 4 AND 6 YEARS

This study investigates the origins of hand preference at 4 years in a cohort of 115 high risk and premature infants: the relationship betwe en patterns of hand preference and intellectual, motor. temperament an d behavioural status at 4 and 6 years; and evidence for brain injury i n mediating the relationship between hand preference and development d isorder. Increased left hand preference was independently associated w ith extreme prematurity, high neonatal risk, increased numbers of mino r physical anomalies, lowered itellectual and motor abilities, and mor e difficult temperament. These findings supported the presence of intr auterine and neonatal pathological mechanisms leading to left hand pre ference in a small number of children. Neither poor function of the no n dominant hand nor absence of a family history of left handedness cou ld further define this pathological subgroup. Support for pathological mechanisms producing left handedness was found predominately in the i nfants of high birth weight, whereas prevalence of left handedness was increased mainly among the extremely low birth weight infants. In thi s latter group the prevalence of left handedness was also increased am ong children of normal intelligence, suggesting that mechanisms other than brain damage lead to left hand preference in very premature infan ts.