Monitoring for One Kind of Signal in the Presence of Another: The Effects of Signal Mix on Detectability

Abstract

Subjects in a 1-h visual vigilance task looked for the occasional presence of a signal inserted into a sequence of single items which consisted of either (a) homogeneous nonsignals or (b) a mixture of nonsignals and signals of another kind. The experiment also manipulated the nature (and discriminability) of the signal to be detected (two types) and its probability of Occurrence (0.05 or 0.15). Results indicate that signal detectability is impaired by the presence of another kind of signal, the impairment tending to be greater the lower the detectability of the signal considered on its own. But, due to a concomitant increase in response bias, the impairment is not reflected in correct detection. The presence of the second signal did not influence the extent of the within-session decline in detection, and the effect of signal probability on detection levels failed to emerge. The practical implications of the findings are discussed.

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References

Adams, J. A. Experimental studies of human vigilance United States Air Force ESD Technical Documentary Report No. 63–320, 1963.

Baddeley, A. D. and Colquhoun, W. P.

Signal probability and vigilance: A re-appraisal of the signal-rate effect

British Journal of Psychology, 1969, 60. 169–178.

Craig, A. Signal recognition and the probability-matching decision rule. Perception and Psychophysics, 1976 20(3), 157–162.

Craig, A.

Is the vigilance decrement simply a response adjustment towards probability matching?

Human Factors, 1978, 20. 441–446.

Craig, A. Vigilance for two kinds of signal with unequal probability of occurrence. Human Factors, 1979, 21, 647–654.

Craig, A. and Colquhoun, W. P. Vigilance effects in complex inspection. In R. R. Mackie (Ed.) Vigilance: Theory, operational performance and physiological correlates. New York: Plenum, 1977.

Drury, C. G. and Fox, J.G. Human reliability in quality control. London: Taylor and Francis, 1975.

Elliott, E. Perception and alertness. Ergonomics, 1960, 3. 357–364.

Fox, J.G. and Haslegrave, C. M. Industrial inspection efficiency and the probability of a defect occurring. Ergonomics, 1969, 12. 713–721.

10.

Green, D.M. and Swets, J. A. Signal detection theory and psychophysics. New York: Wiley, 1966.

11.

Howell, W. C , Johnston, W. A. , and Goldstein, I. L. Complex monitoring and its relation to the classical problem of vigilance. Organizational Behavior and Human Performance, 1966, 1, 129–150.

12.

Kibler, A. W. The relevance of vigilance research to aerospace monitoring tasks. Human Factors, 1965, 7, 93–99.

13.

Konz, S. and Osman, K. Team efficiencies on a paced visual inspection task. Journal of Human Ergology, 1977, 6, 111–119.

14.

Mackworth, J. F. Vigilance and attention. Harmondsworth, U.K.: Penguin Books, 1970.

15.

Megaw, E. D. , Alexander, C. J. , and Richardson, J. Fault mix and inspection performance. International Journal of Production Research, 1979, 17.

16.

Sheehan, J. J. and Drury, C. G. The analysis of industrial inspection. Applied Ergonomics, 1971, 2(2), 74–78.

17.

Smith, G. L. Inspector performance on microminiature tasks. In C. G. Drury and J. G. Fox (Eds.) Human reliability in quality control. London: Taylor & Francis, 1975.

18.

Swets, J. A. Signal detection theory applied to vigilance. In R. R. Mackie (Ed.) Vigilance: Theory, operational performance and physiological correlates New York: Plenum, 1977.