Abstract
Three strategies have been proposed for locomotor interception: the pursuit strategy keeps target-heading constant at zero; constant target-heading strategy (CTH) keeps target-heading constant at a certain value; at last, constant bearing strategy (CB) keeps the target at a constant bearing angle relative to an allocentric reference axis. Numerous studies have tested these strategies in tasks where participants controlled only locomotion speed along a fixed straight path. This task constraint makes it impossible for subjects to use the pursuit strategy, and it does not allow discriminating between the CB and the CTH strategies since any change in bearing angle is equivalent to a change in target-heading angle. In two experiments we tested these strategies by asking participants to steer a car to intercept a moving target in three virtual environments: the plant-wall environment included a textured ground plane with some plants and a wall on it, providing richer visual information about allocentric reference including a reference axis; the textured-ground environment included the bare textured ground plane, providing relatively poorer information about allocentric reference; the green-ground environment included only a ground plane of solid green, eliminating any visual information about allocentric reference in the environment. Although steering behavior varied among participants, they all brought target-heading to a constant greater than zero, consistent with the CTH strategy rather than the pursuit strategy. Only very few participants steered a linear interception path with a low rate of turning/steering adjustment and change in target's bearing angle – the sign of the CB strategy. This overall pattern of steering was also observed in the green-ground environment, inconsistent with subjects using an allocentric reference frame to intercept moving targets with the CB strategy. Overall, our results suggest that locomotor interception is better accounted for by the CTH strategy rather than the pursuit strategy or the CB strategy.
Meeting abstract presented at VSS 2017