The development of visually guided stepping

Abstract

Adults use vision during stepping and walking to fine-tune foot placement. However, the developmental profile of visually guided stepping is unclear. We asked (1) whether children use online vision to fine-tune precise steps and (2) whether precision stepping develops as part of broader visuomotor development, alongside other fundamental motor skills like reaching. With 6-(N = 11), 7-(N = 11), 8-(N = 11)-year-olds and adults (N = 15), we manipulated visual input during steps and reaches. Using motion capture, we measured step and reach error, and postural stability. We expected (1) both steps and reaches would be visually guided (2) with similar developmental profiles (3) foot placement biases that promote stability, and (4) correlations between postural stability and step error. Children used vision to fine-tune both steps and reaches. At all ages, foot placement was biased (albeit not in the predicted directions). Contrary to our predictions, step error was not correlated with postural stability. By 8 years, children's step and reach error were adult-like. Despite similar visual control mechanisms, stepping and reaching had different developmental profiles: step error reduced with age whilst reach error was lower and stable with age. We argue that the development of both visually guided and non-visually guided action is limb-specific.

Keywords: Development; Posture; Reaching; Stepping; Vision.

Fig. 1

Target shown in green. Foot centroids shown in black. For step and reach error we calculated three error types—Constant error: e.g. signed mean value of distances a, b and c. Absolute error: e.g. unsigned mean value of absolute distances |a|, |b| and |c|. Variable error: e.g. standard deviation of absolute distances |a|, |b| and |c|

Fig. 2

Step error and postural stability. Group means and standard errors for a absolute error; b variable error; c constant medial-lateral error; d constant anterior–posterior error; and e shoulder path length. Values are shown for both vision conditions (on/off) and both directions (ahead/side) at all ages. For medial-lateral error (c): negative values indicate left bias, positive values indicate right bias. For anterior–posterior error (d): negative values indicate backward bias, positive values indicate forward bias

Fig. 3

Reach error. Group means and standard errors for a absolute error; b variable error; c constant medial-lateral error; and d constant anterior–posterior error. Values are shown for both vision conditions (on/off) and both directions (ahead/side) at all ages (6/7/8 years). For medial-lateral error (c): negative values indicate left bias, positive values indicate right bias. For anterior–posterior error (d): negative values indicate backward bias, positive values indicate forward bias