Hand preference and manual midline crossing in 12-month-old infants

Sammanfattning: Previous research has found that hand preference can be detected reliably in infants as young as 6 months of age through the use of reach-grasp tasks. While many studies have targeted their efforts at discerning hand preference in infants younger than 12-months of age, a lack of knowledge about hand preference during the ages of 1-2 years remain. The aim of the present study was to investigate whether 12-month-old infants demonstrate a clear hand use preference during unimanual reaching and grasping. Participants consisted of 54 healthy, full term 12-month-old infants (+2/-2 weeks). Goal objects were placed at a reachable distance, in front of the infants and randomly allocated to either left, midline or right positions. Infant hand choices and the success of each grasp were coded offline from video recordings made of the reach-grasp sessions and an overall lateralisation index (LI) was calculated later for each infant. The results demonstrated that the 12-month-old infants were generally right-preferred. Additionally, almost double the frequency of grasps were accounted for by right hand grasps. Further, a significant right hand preference was found when children reached across the midline to grasp objects. The findings imply that hand preference may be readily observed in the prehension activities of 12-month-old infants, and particularly prominent when reaching across the midline.