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Dual-Task Performance, Perfect Time-Sharing, and the Psychological Refractory Period (PRP) Procedure

Time Sharing Experiments

The study of human multiple-task performance has a long history in cognitive psychology. It is of practical importance because many people, such as air-traffic controllers and airline pilots, must consistently perform multiple tasks well, or suffer catastrophic consequences.

The study of multiple-task performance is of theoretical importance because it places heavy demands on the human information processing system and may provide deep insights into how the system¹s components are functionally organized and implemented. To understand multiple-task performance more fully, we must consider the processing stages required to perform a task. Some of these stages are shown on the next overhead. According to this view, when a task is performed, one must first encode a presented task stimulus, then select the appropriate response to that stimulus, and finally produce the movements required to execute that response.

The Psychological Refractory Period (PRP) Procedure

Successfully performing even relatively easy perceptual-motor tasks requires a series of processing stages. First, one must encode the task stimulus, then select the appropriate response, and finally execute that response. How does dividing one's attention among several concurrent tasks affect these processing stages? One hypothesis is that there is an immutable structural bottleneck in the stage of response selection. According to the response-selection bottleneck (RSB) hypothesis, when the response for one task stimulus is being selected, response selection for the other task must wait. Meyer and Kieras (1997a, 1997b), on the other hand, propose that there is no structural response-selection bottleneck. Rather people have flexible control over the course of secondary task processing.

Most of the evidence for the RSB hypothesis comes from studies using the psychological refractory period (PRP) procedure. This procedure, with its emphasis on a primary task at the expense of a secondary task, may cause subjects to adopt a response-selection bottleneck strategy when it otherwise might not be necessary. In these studies we use a dual-task procedure that encourages subjects to process each task independently and discourages the use of a bottleneck strategy. Results suggest that humans have a profound ability to process tasks independently in certain dual-task situations.

For more information:

  • Kieras, D. E., Meyer, D. E., & Ballas, J. (2001). Towards demystification of direct manipulation: Cognitive modelsing charts the gulf of execution. Proceedings of The CHI2001 Conference on Human Factors in Computing Systems (pp. 128-135). New York: Association of Computing Machinery, 2001.

  • Meyer, D. E., Glass, J. M., Mueller, S. T., Seymour, T. L., & Kieras, D. E. (2001). Executive-process interactive control A unified computational theory for answering twenty questions (and more) about cognitive aging. European Journal of Cognitive Psychology, 13(1-2), 123-164.

  • Schumacher, E. H., Seymour, T. L., Glass, J. M., Fencsik, D. E., Lauber, E. J., Kieras, D. E., & Meyer, D. E. (2001). Virtually perfect time sharing in dual-task performance: Uncorking the central cognitive bottleneck. Psychological Science, 12 (2), 101-108.

  • Glass, J. M., Schumacher, E. H., Lauber, E. J., Zurbriigen, E. L., Gmeindl, L., Kieras, D. E., & Meyer, D. E. (2000). Aging and the Psychological Refractory Period: Task-Coordination Strategies in Young and Old Adults. Psychology and Aging, 15, 571-595.

  • Meyer, D. E., & Kieras, D. E. (1999). Precis to a Practical Unified Theory of Cognition and Action: Some Lessons from EPIC Computational Models of Human Multiple-Task Performance. In D. Gopher & A. Koriat (Eds.) Attention and Performance XVII. Cognitive Regulation of Performance: Interaction of Theory and Application. (pp. 17-88). Cambridge, MA: MIT Press, 1999.

  • Schumacher, E. H., Lauber, E. J., Glass, J. M., Zurbriggen, E. L., Gmeindl, L., Kieras, D. E., & Meyer, D. E. (1999). Concurrent Response-Selection Processes in Dual-Task Performance: Evidence for Adaptive Executive Control of Task Scheduling Journal of Experimental Psychology: Human Perception and Performance, 25, 791-814.

  • Meyer, D. E., & Kieras, D. E. (1997). A computational theory of executive cognitive processes and multiple-task performance: Part 1. Basic Mechanisms. Psychological Review, 104, 3-65.

  • Meyer, D. E., & Kieras, D. E. (1997). A computational theory of executive cognitive processes and multiple-task performance: Part 2. Accounts of psychological refractory-period phenomena. Psychological Review, 104, 749-791.

  • Meyer, D.E., Kieras, D.E., Lauber, E., Schumacher, E.H., Glass, J., Zurbriggen, E., Gmeindl, L., & Apfelblat, D. (1995). Adaptive executive control: Flexible multiple-task performance without pervasive immutable response-selection bottlenecks. Acta Psychologica, 90, 163-190.

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