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Unformatted text preview: Research Article How Dogs Navigate to Catch Frisbees Dennis M. Shaffer, 1 Scott M. Krauchunas, 2 Marianna Eddy, 2 and Michael K. McBeath 3 1 Arizona State University West, 2 Saint Anselm College, and 3 Arizona State University ABSTRACT— Using micro-video cameras attached to the heads of 2 dogs, we examined their optical behavior while catching Frisbees. Our findings reveal that dogs use the same viewer- based navigational heuristics previously found with baseball players (i.e., maintaining the target along a linear optical tra- jectory, LOT, with optical speed constancy). On trials in which the Frisbee dramatically changed direction, the dog maintained an LOTwith speed constancy until it apparently could no longer do so and then simply established a new LOT and optical speed until interception. This work demonstrates the use of simple control mechanisms that utilize invariant geometric properties to accomplish interceptive tasks. It confirms a common inter- ception strategy that extends both across species and to complex target trajectories. With little training, dogs can be remarkably good at chasing and catching airborne objects like Frisbees, even when the objects travel through complex trajectories that may dramatically change directions. In the present study, we tested whether dogs utilize the same simple viewer-based navigational heuristics that have been established for human baseball fielders catching fly balls (McBeath, Shaffer, & Kai- ser, 1995a, 1996; McLeod & Dienes, 1993, 1996; McLeod, Reed, & Dienes, 2001; Michaels & Oudejans, 1992; Shaffer & McBeath, 2002). Using these heuristics, a pursuer controls the geometric rela- tionship between him- or herself and the target, maintaining an optical image of the target that travels along a straight-line, constant-speed trajectory. We refer to these geometric relationships as optical line- arity and optical speed constancy, respectively. Behavior consistent with the maintenance of optical linearity and speed constancy has been found in a variety of navigation-related domains (Adams, 1961; Bruce, Green, & Georgeson, 1996, pp. 267–285; Roscoe, 1968; Toates, 1975, pp. 151–257; Vishton & Cutting, 1995; Wickens, 1992, pp. 466–481). In the experiment reported here, we investigated whether nonhuman species intercepting targets use the same simple control mechanisms that baseball outfielders use to catch fly balls. When baseball outfielders run to catch fly balls, they use natural, geometrically invariant properties to optically maintain control over the balls. When balls are headed off to the side, fielders select a running path that maintains a linear optical trajectory (LOT) for the ball relative to home plate and the background scenery. In our pre- vious work, we found evidence indicating that the optical information available to the outfielder can be simply analyzed by examining it as a unified two-dimensional (2D) optical image. The geometry of the unified 2D optical image is shown in the top left panel of Figure 1,...
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- Spring '09
- Trajectory, Trajectory of a projectile, Vertical direction, optical trajectory, vertical optical angle