Motor Skill

Infants acquire basic motor skills–reaching, sitting, crawling, and walking–against a backdrop of dramatic body growth and immense amounts of experience in a changing environment. We found that practice crawling and walking explains more variance in the characteristic improvements in locomotor skill than do infants’ body dimensions and chronological age. Practice is not rote repetition. Rather, general experience with new action systems facilitates widespread improvements (e.g., practice belly crawling facilitates crawling on hands and knees, despite differences in the body parts used for support and propulsion and differences in interlimb coordination).

Currently, we are comparing infants’ and adults’ abilities to adapt to changes in their body dimensions using various motion recording devices to track participants’ movements (gait carpet, electrogoniometers, Optotrak). We experimentally induce body asymmetries with a platform shoe to elongate one leg while walking or marching; lead-weighted packs on the front, back, or sides of the body during load carriage; and a tilt board that shifts infants’ weight forward, backward, or sideways while sitting. We observe how pregnant women adapt to sudden growth changes as they walk through apertures and we simulate growth changes by increasing the size of participants’ abdomens or shoulders with “pregnancy” pouches or “football player” shoulder pads and their hands with neoprene gloves as they walk, crawl, or reach through apertures. In some cases, variability in infants’ movements reaps surprising benefits–greater plasticity in the face of perturbations–and automaticity of adults’ movements comes at a cost–inability to adapt to novel challenges. In other cases, infants can only accommodate to novel force distributions while adults can compensate for the change in their bodies by shifting their weight in the direction opposite to a load.