Faculty Bibliography

In 2 experiments the authors demonstrated that adaptive locomotion can involve means-ends problem solving. Sixteen-month-old toddlers crossed bridges of varying widths in the presence or absence of a handrail. Babies attempted wider bridges more often than narrow ones, and attempts on narrow bridges depended on handrail presence. Toddlers had longer latencies, examined the bridge and handrail more closely, and modified their gait when bridges were narrow and/or the handrail was unavailable. Infants who explored the bridge and handrail before stepping onto the bridge and devised alternative bridge-crossing strategies were more likely to cross successfully. Results challenge traditional conceptualizations of tools: Babies used the handrail as a means for augmenting balance and for carrying out an otherwise impossible goal-directed task.

This study compared the relative contributions of growing body dimensions, age, and walking experience in the development of walking skill in 9- to 17-month-old infants (N = 210), 5-6-year old kindergartners (N = 15), and college students (N = 13). Kinematic measures derived from participants' footprints showed characteristic improvements in walking skill. As children became bigger, older, and more experienced, their steps became longer, narrower, straighter, and more consistent. Improvements reflected a narrowing base of support and increasing control over the path of progression. Although both infants' age and the duration of their walking experience contributed to improvements in walking skill, experience was the stronger predictor. This finding suggests that practice is the more important developmental factor for helping infants to conquer their weak muscles and precarious balance.

Based on studies with infants, we expand on Stoffregen & Bardy's explanation of perceptual motor errors, given the global array. Information pick-up from the global array is not sufficient without adequate exploratory movements and learning to support perceptually guided activity.

We propose a sequential process of exploration that can account for perception-action coupling in infant locomotion. Each phase in the sequence is a process of obtaining progressively more information leading to a motor decision - exploration from a distance, exploration via direct contact, and exploration of alternative means. Quick glances and prolonged looking from afar serve to alert the perceiver to important changes in the terrain. Intentional touching and testing alternative ways to traverse an obstacle are only prompted when prior information indicates a potential threat to balance. We further propose that depth information is privileged because it can be detected from a distance more readily than other surface properties such as rigidity and friction. Studies of infants walking down slopes and across "hole/patch" transitions illustrate the important role of exploration in prospective control of locomotion. © 2001 Elsevier Science Inc.