The role of locomotor posture and experience on handedness and footedness in infancy

This research examined the development of handedness and footedness in infancy. We measured footedness by documenting the limb infants used to “lead-out” as they crawled or walked down a path several times. We measured handedness by documenting the hand infants used to reach for a goal at the end of each trial. Study 1 showed that locomotor skill affects limb lateralization preferences and that most 13-month-old infants demonstrated a side preference for reaching and leading out “in the moment.” Study 2 longitudinally examined the developmental trajectories of handedness and footedness as they related to locomotor posture and experience. The findings suggest high variability in the developmental trajectory of footedness, with frequent fluctuation between side preferences. The developmental trajectory of handedness was more stable over the transition between locomotor milestones. The transition between crawling and walking decreased the proportion of infants demonstrating side preferences for leading out and the onset of walking decreased the proportion of infants demonstrating side preferences for reaching. These findings demonstrate the importance of making behavioral observations at multiple time scales to understand underlying developmental trajectories, specifically the stability or instability of the motor system associated with the acquisition of new motor abilities.

► Locomotor posture and experience affect manual and pedal lateralization. ► Walking onset decreases number of infants with a hand preference for reaching and increases the number of infants with a preference for reaching with both hands. ► The crawl-to-walk transition decreases foot preference for leading-out. ► Manual and pedal lateralization develop on different time scales.