Scheduled for Motor Behavior and Measurement Posters, Wednesday, April 2, 2003, 1:00 PM - 2:00 PM, Convention Center: Exhibit Hall A


Influence of the Direction of an Approaching Stimulus on Coincident Timing

Cheryl Coker, New Mexico State University, Las Cruces, NM

In many skills requiring coincident timing, a stimulus can approach a performer from a number of directions. Examining the influence of stimulus direction on coincident timing Payne (1987) found that significantly less error resulted when a stimulus approached performers directly from the front as opposed to either the left or right sides. Recently however, Williams et al (2001) found that the coincident timing error of simple movements, such as a finger press task, were significantly less than for larger, more complex movements. Given that the task used in Payne's study was a simple finger press task, further exploration into the influence of stimulus direction using more complex tasks is warranted. Consequently, the purpose of this study was to investigate the influence of direction of an approaching stimulus on the coincident timing of a ballistic striking task. Twenty-six right hand dominant subjects performed a 60cm horizontal arm motion to displace a wooden barrier in coincidence with the final light in a series that traveled down a runway. Twenty trials were randomly performed at each of two stimulus velocities, 4 and 8 mph, which approached from either the left or the right of the subject. Initial stimulus direction was counterbalanced across subjects. Separate 2x2 (direction x speed) ANOVAs with repeated measures on both factors were performed for initiation time, movement time, response accuracy, response consistency and response bias. No significant differences were found for direction of approaching stimulus. Significant effects were however, found for speed. Not surprisingly, significantly faster response initiations and movement times were recorded for the 8 mph stimulus. Data for response bias indicated that the timing error was generally late regardless of stimulus velocity. In addition, responses performed at the 4mph stimulus speed were significantly more accurate than those at 8 mph. This finding contradicts current literature. Finally, no significant differences were reveled for response consistency. Consequently, the results of this study concur with the findings of Payne (1987) in that the direction of an approaching stimulus does not appear to influence the coincident timing of a ballistic striking action.

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