Initial-state dependency of learning in young infants.

With the aim of investigating the effect of the initial state of pre-learning on subsequent infant learning (i.e., the initial-state dependency), we observed the limb movements in 3-month-old infants in the course of a motor learning task. The session comprised 2-min pre-learning and 4-min learning periods, and the infants learned to move a toy using a string attached to either an arm (arm-based learning, Experiment 1) or a leg (leg-based learning, Experiment 2). Infants were assigned to low- and high-state groups in the initial-state condition according to the average velocity of the arm (Experiment 1) or leg (Experiment 2) movements during the pre-learning period. The results revealed that, during the learning period, infants in the low-state group increased the movement of their limbs, whereas those in the high-state group showed no significant changes in the movement of most of their limbs. These results suggest that infants demonstrating a low average velocity of movement in the initial state easily observed and learned the circular causality between self-produced movements and environmental changes. On the other hand, it seemed that infants demonstrating a high average velocity of movement in the initial state could not or did not need to increase their limb movements (the toy would already be shaking enough to form striking movements).