The purpose of this study was to analyse infants' and toddlers' manual preference in reaching objects of different sizes and rigidity at the ages of 4, 6, 8, and 36 months. Four objects of different size and stiffness were presented to nine healthy infants leaning on a chair at 50º. A total of 524 reaching movements were analysed longitudinally to verify manual preference and the index of contribution of each hand for bimanual reaching. Results showed preference of the right hand for reaching objects; only at the age of 6 months the object size influenced manual preference: infants used preferably the right hand to reach small objects and the left one for large objects. The hand that first touched the object in bimanual reaching was the most active during reaching trajectory. These findings suggest that the size of the object - and not rigidity, which is less visually perceptible - influenced infants' reaching at the age of 6 months, that is, when reaching movement is being refined; small objects, which require more accuracy to be grasped, were reached with the right hand (preferred one)), whereas large objects which do not require accuracy to be grasped were reached with the left hand.
Functional laterality; Infants and toddlers; Motor activity; Movement, reaching
