Timing Is Almost Everything: How Children Perceive and Act on Dynamic Affordances.

A key challenge for the developing perception-action system is learning how to move the self in relation to other moving objects. This often involves perceiving and acting on affordances or possibilities for action that depend on the relation between the characteristics of the individual and the properties of the environment (Gibson, 1979). This chapter overviews our program of research on perceiving and acting on dynamic affordances (i.e., possibilities for action that vary over time). Our goal is to bridge the divide between basic and applied research by using road crossing as a model system for studying how children's ability to perceive and act on dynamic affordances undergoes change with age and experience. The basic task is for participants to cross virtual roads with continuous traffic either on foot or on a bicycle. This work reveals that children's gap choices and crossing motions are less tightly linked than those of adults. Children often choose the same size gaps as adults but time their entry into those gaps less tightly than adults. As a result, children typically end up with less time to spare than adults when they clear the path of the vehicles. Improvement in gap selection and movement timing occurs gradually over development, indicating the perception-action system undergoes continuous change well into adolescence. As in other areas of development (e.g., face perception, word recognition), this kind of gradual developmental change appears critical for the fine-tuning of the system. The late development of these skills may explain also why adolescent pedestrians, cyclists, and drivers continue to be at risk for collisions when crossing roads. Further work aimed at better understanding the developmental mechanisms underlying these changes will inform the fields of both developmental science and injury prevention.