Description of Work
The first of my active programs of research serves to gain empirical knowledge of the low-level visual sensory information used to generate the motor behavior used to pursue targets, and the higher-level mental representations people have of the flight of these targets as they pursue them. That is, I investigate how we turn physical information in the world into usable perceptual information to navigate through the world, and whether the same sensory information that guides our motor behavior forms our conscious perceptions. This program of research first focuses on the pursuit strategies that humans and animals use to visually track and pursue various targets. My previous and current research describes how outfielders and dogs utilize sensory information to guide motor behavior as they pursue fly balls and Frisbees. The results of several experiments support that they take advantage of the relative angle of motion between themselves and the ball that can be used generically to pursue and approach moving objects. This program of research has important implications for developing geometrically invariant strategies of pursuit for target interception and avoidance in the robotic, nautical, aeronautical and ballistic domains.
Shaffer, D. M., & McBeath, M. K. (2005). Naive beliefs in baseball: Systematic distortion in perceived time of apex for fly balls. Journal of Experimental Psychology: Learning, Memory, & Cognition, 31, 1492-1501.
Shaffer, D. M., McBeath, M. K., Roy, W. L., & Krauchunas, S. M. (2003). A LOT is required to run to the side to catch fly balls. Journal of Experimental Psychology: Human Perception and Performance, 29, 1244-1250.
Shaffer, D. M., & McBeath, M. K. (2002). Baseball players maintain a linear optical trajectory when tracking uncatchable fly balls. Journal of Experimental Psychology: Human Perception and Performance, 29, 335-348.
McBeath, M. K., Sugar, T. G., & Shaffer, D. M. (2001). Comparison of active versus passive ball catching control algorithms using robotic simulations. Journal of Vision, 1, 193a, http://journalofvision.org/1/3/193, doi: 10.1167/1.3.193.
McBeath, M. K., Shaffer, D. M., & Kaiser, M. K. (1996). On catching fly balls. Science, 273, 256-260.
McBeath, M. K., Shaffer, D. M., & Kaiser, M. K. (1995). Play ball! Science, 268, 1683-1685.
McBeath, M. K., Shaffer, D. M., & Kaiser, M. K. (1995). How baseball outfielders determine where to run to catch fly balls. Science, 268, 569-573.
Although baseball outfielders are generally good at utilizing the sensory information for accurate guidance of locomotion through the world, their conscious perceptions about what the ball flight looks like to them as they run to intercept balls are not consistent with the physical information available to them. In several studies I have examined how expert and novice baseball players confound the information actually available to them with their more extensive mental representation of the information they think they have available to them that incorporates a reasonable understanding about the physical flight of the ball.
Shaffer, D. M., Krauchunas, S. M., Eddy, M., & McBeath, M. K. (2004). How dogs navigate to catch Frisbees. Psychological Science, 15, 437-441.
Videos of Participants Trying to Determine the Apex of Fly Balls
Another of my active programs of research serves to gain knowledge of the brain systems underlying visual tracking. This research focuses on the neural mechanisms underlying prediction and anticipation in sensorimotor systems. I have investigated how prediction and attention affect visual tracking by measuring different types of eye movements to targets varying in velocity and predictability. I am currently applying this line of research to the situation when humans are free to move about in their environment. The results of these experiments will be the basis of developing the movement of cameras used to control an omni-directionally movable robot programmed to track and pursue targets in three dimensions.
Shaffer, D. M., Krisky, C. M., & Sweeney, J. A. (2003). Frequency and metrics of square wave jerks: Influence of task demand characteristics. Investigative Ophthalomology and Visual Science, 44, 1082-1087.