Spatially constrained locomotion under informational conflict.

This study investigates the informational based that supports intentional adaptation of locomotion to spatial environmental constraints. A virtual reality setup was used to present subjects with targets providing normal as well as abnormal optical expansion during locomotor pointing (i.e. positioning of a foot on a visible target on the floor during walking). The manipulation dissociated two variables providing temporal information about time-to-passage (TTP): TTP(beta alpha) which encompasses target expansion, and TTP(alpha) which is independent of target expansion. While a previous study showed TTP(alpha) to be sufficient, the present results reveal that TTP(beta alpha) may be used when it is available. This finding indicates that both variables play a role that varies according to the circumstances. Furthermore, the present results provide evidence of the operation of a security principle for action in conflicting situations.