Abstract
INTRODUCTION: The natural walking environment is cluttered and changeable. For safety and efficiency, the feet must be placed precisely, into tightly constrained locations. This requires both sensitivity and responsivity to visual cues about the environment. By 8 years, children use visual information to guide single, precise steps in an adult-like way (Mowbray et al, 2019). But do children of this age benefit from distal visual cues about the upcoming terrain during walking? Do children plan ahead like adults (Matthis et al, 2018)? Or do they control walking one step at a time, using proximal visual cues?
METHODS: Adults (N=30) and 8 year olds (N=30) walked across a series of stepping targets in virtual reality. We manipulated the number of visible upcoming targets to 1, 2 or 3 steps ahead. Participants also completed a virtual single-step task. We used motion capture to record speed and step error.
RESULTS: Both children and adults walked more slowly when vision was restricted to just one step ahead F(2, 116)=6.172, p=.005. Children’s error was higher than adults for single steps F(1, 58)=23.049, p<.001, and was consistently higher than adults’ during walking - regardless of visual condition F(1, 58)=135.202, p<.001. Adults showed higher error when given more visual information about the upcoming terrain F(2, 58)=5.1, p=.009.
CONCLUSIONS: Given more visible upcoming targets, both adults and children walk more quickly. Adults show an accompanying increase in foot placement error. For children, foot placement error is consistently high across conditions. We conclude that 8 year olds do use distal cues to select appropriate walking speed. However, children are unable to use distal visual cues to adjust step accuracy. In summary, at self-selected speed, both children and adults walk more slowly when they are unable to plan ahead. For adults only, this allows better control of foot placement error.