Visual Guidance of Intercepting a Moving Target on Foot

Abstract

How do people walk to a moving target, and what visual information do they use to do so? Under a pursuit strategy, one would head toward the target's current position, whereas under an interception strategy, one would lead the target, ideally by maintaining a constant target-heading angle (or constant bearing angle). Either strategy may be guided by the egocentric direction of the target, local optic flow from the target, or global optic flow from the background. In four experiments, participants walked through a virtual environment to reach a target moving at a constant velocity. Regardless of the initial conditions, they walked ahead of the target for most of a trial at a fairly constant speed, consistent with an interception strategy (experiment 1). This behavior can be explained by trying to maintain a constant target-heading angle while trying to walk a straight path, with transient steering dynamics. In contrast to previous results for stationary targets, manipulation of the local optic flow from the target (experiment 2) and the global optic flow of the background (experiments 3 and 4) failed to influence interception behavior. Relative motion between the target and the background did affect the path slightly, presumably owing to its effect on perceived target motion. We conclude that humans use an interception strategy based on the egocentric direction of a moving target.

Cortical dynamics of navigation and steering in natural scenes: Motion-based object segmentation, heading, and obstacle avoidance

“…The STARS model (Elder et al, 2007) did not explain the interception of moving targets. Fajen and Warren (2004) have demonstrated that humans tend to take an interception strategy that is somewhere between a pursuit strategy, where the target path is followed, and a constant bearing strategy, where a minimal path to the intersection point of the observer path with the target path is taken. Fajen and Warren (2004) required extensive updates to their 2003 model in order to explain these data.…”

“…Fajen and Warren (2004) have demonstrated that humans tend to take an interception strategy that is somewhere between a pursuit strategy, where the target path is followed, and a constant bearing strategy, where a minimal path to the intersection point of the observer path with the target path is taken. Fajen and Warren (2004) required extensive updates to their 2003 model in order to explain these data. Dessing, Peper, Bullock & Beek (2005) demonstrated how visually derived information can be used to catch a moving ball.…”

Steering by Hearing: A Bat’s Acoustic Gaze Is Linked to Its Flight Motor Output by a Delayed, Adaptive Linear Law

“…This finding can be used to consider the generality of theories of sensory-locomotion coordination based on studies of visual animals. For humans, the relationship between gaze direction and motion has been interpreted in the context of visual cues such as optic flow (Wann and Swapp, 2000;Warren et al, 2001;Wilkie and Wann, 2003;Fajen and Warren, 2004). One leading hypothesis is that a visually guided animal steers by centering the focus of expansion (FOE) of optic flow on a locomotor goal (Gibson, 1950(Gibson, , 1966.…”

Minimum jerk for human catching movements in 3D

“…If, while standing on one ship one observes another ship on the horizon at a particular azimuth with respect the current heading, and if after a period of time in which the boats move forward along constant heading the azimuth remains the same, one can be assured that the two boats are on a collision course. To intercept the ball in a soccer match one could run forward while adjusting the speed such that the azimuth of the ball with respect to the player remains constant [5]. Similar strategies can be used to run forward or backwards on the playing field to catch a fly ball [16].…”