Academic journal article Canadian Journal of Experimental Psychology

Target Speed Alone Influences the Latency and Temporal Accuracy of Interceptive Action

Academic journal article Canadian Journal of Experimental Psychology

Target Speed Alone Influences the Latency and Temporal Accuracy of Interceptive Action

Article excerpt

Abstract When intercepting a mobile object or an apparent movement, participants show a temporal bias. They are in advance when dealing with a slow-moving stimulus and late with a fast-moving one. We studied participants intercepting an apparent movement by sliding a disk on a table. Using a fast and a slow stimulus speed, we varied three factors: duration of presentation of the stimulus, distance covered by the stimulus, and speed context (constant or varied) of stimulus presentation. In addition to the temporal bias, spatial accuracy and kinematic measures were collected. The temporal bias created by speed was evident across all three factors. Speed, in addition to strongly determining the temporal bias, significantly affected the throwing strategy adopted by the participants, as revealed by latency, movement time, and disk trajectory duration.

An interception or coincidence-anticipation task generally consists of coordinating two distinct events: individual action and environmental fluctuations (Benguigui, 1994). Tresilian (1994) has recently defined coincidence-anticipation as the aptitude to reach, at a given time, the interceptive point of a mobile object in space, an aptitude that Bartlett (1958) has described as "by far the most important characteristic of bodily skill."

It is commonly found that, when intercepting a mobile object or an apparent movement with a complex motion, participants show a temporal bias, i.e., they are in advance when dealing with a slow-moving stimulus and are late with a fast-moving object (e.g., Gagnon, Bard, Fleury, & Michaud, 1991). However, the covariation of stimulus characteristics (duration and length of the stimulus exposure) have yielded divergent findings in the interceptive behaviour literature and raised important issues on stimulus integration and/or information processing.

Attempts to answer the question of how much time is necessary to extract information from a moving stimulus have been made via two approaches: occlusion of part of the trajectory of the moving object and manipulation of stimulus duration or distance covered by the stimulus, and speed. On the one hand, the overall message from experiments using the occlusion paradigm is that even a very brief period of visual tracking of the ball trajectory is sufficient to yield adequate catching performance (Rosengren, Pick, & von Hofsten, 1988; Smyth & Marriott,1982; Whiting, 1968, 1986; Whiting, Alderson & Sanderson, 1973; Whiting, Gill & Stephenson, 1970; Whiting & Sharp, 1974). Lamb and Burwitz (1988), also using the occlusion paradigm, observed better ball catching performances as stimulus exposure duration increased from 100 to 200 ms. Adding time to this "optimal duration" did not improve participants' accuracy.

On the other hand, Shea, Krampitz, Tolson, Ashby, Howard and Husak (1981) and Shea and Northam (1982) demonstrated that the mere reduction of stimulus exposure time (from 671 to 335 ms) yielded an increased accuracy in a press button response, whatever the stimulus speed. Ball and Glencross (1985), in contrast, observed a decreased accuracy in children (5, 7, and 9 year-old), whenever exposure time increased, especially with slow-moving stimulus. Payne's (1986) participants were assigned to one of three experimental conditions (short, medium, and long runway) and were positioned to view a light stimulus runway, which approached them directly from the front. Performance at a simple press button response was measured. No main effect of runway length was observed on the temporal bias, although it had significant effects on absolute and variable errors. Similarly, in a simple discrimination task, Shea and Northam (1982) had participants verbally evaluate variable velocities (away, towards, or across) ranging 44.7 cm/s above and below one of three criteria (134.11, 268.22, and 402.23 cm/s) in 8.94 cm/s increments, using the method of constant stimuli. The participants' orientation to the stimulus and the varying distance (length of runway) played little or no role in the perceptual discrimination process. …

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