This article applies to:
Experiment Author: Susan Campbell. Adapted from STEP and used with permission of Brian MacWhinney
This study shows that there is a response selection bottleneck, but that visual attention is not affected by the bottleneck.
The task used was a speeded response to a tone and an un-speeded report of a letter. The tone was often responded to after the letter appeared, but there did not seem to be any problems with processing the letter as a result, though response to it was slowed by the proximity of the response to the tone.
This experiment plays a low pitch tone or a high pitch tone followed by a 200 millisecond display of a letter array consisting of A-B-C-D. After the tone and array stimulus, participants respond for both audio and visual stimuli. "z" or "x" for a high-tone or low-tone, respectively. Then press "b", "n", "m", or "," for A-B-C-D stimuli. The target letter will be underlined during the stimulus display. The responses must be made as quickly as possible after the letter array has disappeared. There are 90 trials in this experiment.
Pashler, H. (1992). Attentional limitations in doing two tasks at the same time. Current Directions in Psychological Science 1, 44-47.
Cited Experiment Abstract
Beginning with the work of Sherington near the turn of the century, it has emerged that the basic units of the nervous system-the neurons- operate in parallel, with hundreds of millions of neurons firing away simultaneously. But what about mental operations? Can we carry out more than one distinct mental operation in parallel? Or are certain psychological processes restricted to operating one at a time? This article describes some recent experimental studies of what happens when individuals attempt to carry out more than one activity at the same time. The focus is on simple tasks for which the time-course of processing can be analyzed in detail. The results are beginning to reveal something of the underlying processing limitations of the mind and imply surprisingly severe and stubborn limits on what mental activities people can accomplish at the same time. The results also suggest that speaking of attention as a single mental resource or capacity is misleading because several quite distinct processing limitations exist, each of which -in its own way- restricts our ability to carry out more than one task at a time.
Works Cited by the Experiment
Carrier, M., & Pashler, H. (1991). The attention demands of memory retrieval. unpublished manuscript, University of California-San Diego, La Jolla.
Duncan, J. (1984). Selective attention and the organization of visual information. Journal of Experimental Psychology: General, 113, 501-517.
Fagot, C., & Pashler, H. (in press). Making two responses to a single object: Implications for the central attentional bottleneck. Journal of Experimental Psychology: Human Perception and Performance.
McCann, R., & Johnston, J.C. (in press). The locus of the single channel bottleneck in dual task interference. Journal of Experimental Psychology: Human Perception and Performance.
Osman, A., & Moore, C. (November 1990). Locus of the single-channel bottleneck, paper presented at the Psychonomic Society Meetings, New Orleans.
Pashler, H. (1984). Processing stages in overlapping tasks: Evidence for a central bottleneck. Journal of Experimental Psychology: Human Perception and Performance, 10, 358-377.
Pashler, H. (1989). Dissociations and dependencies between speed and accuracy: Evidence for a two-component theory of divided attention in simple tasks. Cognitive Psychology, 21, 469-514.
Pashler, H. (1991). Shifting visual attention and selecting motor responses: Distinct attentional mechanisms. Journal of Experimental Psychology: Human Perception and Performance, 17, 1023-1040.
Pashler, H., & Christian, C. (1991). Dual-task interference and the production of motor responses, unpublished manuscript. University of California-San Diego, La Jolla.
Pashler, H., & Johnston, J.C. (1989). Interference between temporally overlapping tasks: Chronometric evidence for central postponement with or without response grouping. Quarterly Journal of Experimental Psychology, 41A, 19-45.
Pashler, H., Luck, S., Hillyard, S., Mangus, R., Gazzaniga, M., & O'Brien, S. Sequential operation of the cerebral hemispheres in "split-brain" patients, unpublished manuscript. University of California-San Diego, La Jolla (1991).
Posner, M., Inhof, A., Friedrich, F., & Cohen, A. (1987). Isolating attentional systems: A cognitive-anatomical analysis. Psychobiology, 15, 107-121.
Smith, M.C. (1967). Theories of the psychological refractory period. Psychological Bulletin, 67, 202-213.
Welford, A.T. (1952). The "psychological refractory period" and the timing of high-speed performance - A review and a theory. British Journal of Psychology, 43, 2-19.