Hesitations in Continuous Tracking Induced by a Concurrent Discrete Task

Abstract

Subjects performed continuous, visually guided pursuit tracking with the right hand while giving simultaneous discrete left-hand responses, which were signaled by auditory tones appearing at the average rate of one tone per 30 s. This left-hand secondary task was frequently associated with tracking hesitations lasting 333 ms or longer. The rate of occurrence of these hesitations was about the same when the left-hand response involved a choice between competing responses as when the left hand responded in a previously specified direction. Hesitations occurred for three different mechanical tracking manipulanda using different controlling muscles and appeared to be due to active muscular freezing rather than to relaxation. The rate of hesitations declined with practice, and this improvement in right-hand performance was accompanied by an improvement in performance of the concurrent left-hand response.

Resource scarcity and outcome conflict in time-sharing performance

“…Klapp et al (1987) found the frequency of tracking holds and holds of long duration to decrease with increased tracking priority. Tsang and Wickens (1988) found that subjects were better able to protect the primary task in the manual-manual task pairs than in the manual-speech task pairs from error spikes, despite a greater level of interference (larger dual-task performance decrement) in the manual-manual task pairs.…”

“…Yet, they all reported clear dual-task interference, provided that the tasks were sufficiently difficult (Cliff, 1973;Tsang & Wickens, 1988;Vidulich, 1990). Interference was observed between two visual tasks (Fracker & Wickens, 1989;Onstott, 1976;Tsang & Wickens, 1988;Vidulich, 1989Vidulich, , 1990, between one visual and one auditory task (Cliff, 1973;Klapp et al, 1987;McLeod, 1977;Netick & Klapp, 1994;Tsang & Wickens, 1988), between two tracking axes controlled by the same hand (Onstott, 1976), between two tasks controlled by two hands (Fracker & Wickens, 1989;Klapp et al, 1987;McLeod, 1977;Netick & Klapp, 1994;Tsang & Wickens, 1988;Vidulich, 1989Vidulich, , 1990, and between two tasks, one controlled manually and one by speech (Cliff, 1973;Tsang & Wickens, 1988). It would be difficult to attribute all of these interferences to peripheral interference due to performing two tasks of the same input modality, of the same output modality, or with the same physical apparatus.…”

“…Five other studies are especially relevant to the present one in that a discrete-continuous task pair was used and relative priority between the time-shared tasks was manipulated. Klapp, Kelly, and Netick (1987) had subjects perform a visual-manual pursuit tracking task and an auditorymanual reaction time task. More tracking holds (hesitations) were observed when the tracking task was performed with the reaction time task than when it was performed without.…”

“…This suggests that the interference occurred primarily during response processing as opposed to the perceptual processing of the stimulus. Because the interference in tracking response was observed to begin prior to the discrete RT, Klapp et al (1987) and Netick and Klapp (1994) argued that the interference arose during the preparation or programming of the response as opposed to during response execution. The interference was attributed to a singlechannel processor that is constrained to programming one response at one time.…”

Evidence for Processing Stages in Skill Acquisition: A Dual-Task Study

“…Interference could result from costs of concurrence (Navon and Gopher 1979), that is, the effort of time-sharing per se or from a competition for control of peripheral inputs and/ or outputs (e.g., Klapp et al 1987). Compelling evidence for a role of resource competition was provided only by one study, which used two levels of LT difficulty (Kramer and Strayer 1988), and two studies that included a nonlearning control for AT (Trumbo et al 1968;Hazeltine et al 1997): Either manipulation should have no effect on time sharing or on peripheral competition; however, both altered the magnitude of dual-task interference, thus supporting the role of resource competition.…”