2, 246-248. Effects of Noise on Performance on Embedded Figures Tasks. Andrew P. Smith and Donald E. Broadbent. University of Oxford, Oxford, England.
Journal of Applied Psychology 1980, Vol. 65, No. 2, 246-248
Effects of Noise on Performance on Embedded Figures Tasks Andrew P. Smith and Donald E. Broadbent University of Oxford, Oxford, England
One explanation of certain noise effects is in terms of increased attentional selectivity. However, the generality of certain results that provide the basis for this view has been questioned by a number of recent studies. The two experiments reported here also suggest that noise will not always influence performance on tasks involving salient and irrelevant cues. In the first experiment, 20 female subjects were tested individually on an embedded figures task in both noise (85 dB [C]) and quiet (55 dB 1C]). Half of the subjects had the noise treatments in the order quiet-noise and half in the order noisequiet. In the second experiment, 32 female subjects were given a more difficult embedded figures task. Neither experiment showed any effect of noise on performance. Broadbent (1971) has suggested that one of the effects of noise is an increase in the probability of sampling from dominant sources. This has been shown to be the case in dual-task situations (Hockey, 1970a, 1970b) and in cases in which conflicting relevant and irrelevant stimuli are involved (e.g., the Stroop Color-Word Interference Test). However, the attention-deployment view of noise effects has not been supported by some recent results. Forster and Grierson (1978) and Loeb and Jones (1978) found no effect, or the opposite effect to Hockey's, when using a tracking and monitoring task. The existing literature on the effects of noise on the Stroop task is also conflicting. Some authors have reported that performance on the interference task is better in noise (e.g., Houston, 1969; Houston & Jones, 1967), whereas others have found the opposite effect (e.g., Hartley & Adams, 1974, Experiment 1). Indeed, the effects probably depend on the relative salience of the words and colors rather than on a change in interference per se. (See Broadbent, Note 1, for a further discussion of this point.) The experiments described in this article were designed to investigate the effects of noise on another task involving relevant and irrelevant cues—the embedded figures task. Callaway The first author was supported by the British Social Science Research Council; the second author is employed by the Medical Research Council. Requests for reprints should be sent to Donald E. Broadbent, Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, England.
(1959) found that performance was better on an embedded figures task following administration of the stimulant drugs amobarbital and methamphetamine. Oilman (1964) has also reported that white noise increases field independence. However, he used a rod and frame test as a measure of field independence, and it has been shown that there is only a moderate correlation of .4-.6 between this and certain embedded figures tasks (Arbuthnot, 1972). The details of the level of noise are not clear from his report, and as noise was always given second, it is not clear whether the reported effect is solely due to noise or, to some extent, to practice. It is desirable to carry out further studies on the effects of noise on embedded figures tasks. The following experiments used different versions of embedded figures tasks to see whether noise would aid performance on them and to see whether any noise effects were general or dependent on certain features of the tasks. Experiment 1 Method Each subject carried out an embedded figures task in noise and quiet conditions. Half of the subjects had the noise treatments in the order noise-quiet and half in the order quiet-noise. The subjects were tested in groups of 5, and the noise and quiet conditions were 1 week apart. The subjects were 20 female members of the Oxford Subject Panel, and they were paid for participating in the experiment. The average age of the subjects was 34.5 years (SD = 7.5 years; range = 20-46 years).
Copyright 1980 by the American Psychological Association, Inc. 0021-9010/80/6502-0246S00.75
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Continuous noise was used with equal levels per octave (±1 dB) from 125-4000 Hz. The sound level in the noise condition was 85 dB (C). In the quiet condition, the sound level was 55 dB (C). The embedded figures task was based on figures shown in the University of Toronto Health Sciences Hidden Figures Test. However, this was modified in the following way. At the top of each sheet of paper were 5 simple figures labelled A-E. Below these were a series of more complex figures. Above each complex figure was a letter denoting which simple figure was present in it. There were 32 test figures on the sheet. On one session subjects did the odd-numbered figures and on another the even-numbered figures. Half of the subjects did the figures in the order odd-even and half in the order even-odd. A pilot study had suggested that the two sets of figures were of comparable difficulty. The subjects were given the following written instructions: In this task you have to find a simple figure in a more complex pattern. The 5 simple figures are labelled A-E. The actual simple figure that is present in a particular complex figure is written above the figure. Your task is to find the simple figure and shade it in. There is only one simple figure in each pattern and this figure will always be in the right side up and exactly the same size as one of the simple figures. If you get stuck on a particular figure go on to the next. Turn over the page when you have completed one side. If you have any questions about the task please ask me.
The subjects were then shown a completed sample of what they had to do. They were then given 8 minutes to complete as many figures as possible (maximum = 16). Results The mean number of figures completed was 8.40 in noise and 8.45 in quiet. An analysis of variance revealed that this difference failed to reach significance (F < 1). As an index of the power of the experiment, a difference of 1.313 would have been significant. Indeed, the only influence on performance was practice, F(l, 18) = 13.05, p = .002. On the second session 9.55 figures were detected and on the first only 7.30. The noise did not interact with this practice effect. Subjects completed more even numbered figures than odd (8.7 vs. 8.15), but this difference was not significant. Individual differences in ability of the subjects to do the task were large compared with differences between conditions. The scores ranged from 1 to 16, SD
= 6.005. However, when the subjects were divided into high and low scorers, there was still no effect of noise on either group. A negative correlation was found between age and number of embedded figures completed (tau = -0.37), but there was no significant correlation between age and the noise effect for either the quiet-noise group of subjects or the noise-quiet group of subjects. Experiment 2 Method This experiment was similar to the previous one except that the embedded figures task was modified. In this version of the task, the subjects were shown the simple and complex figures but were not told which of the simple figures was present in each complex figure. The only other differences were that the subjects were tested individually and that the task lasted for 10 minutes. The subjects were 32 female members of the Oxford Subject Panel. The average age of the subjects was 33.8 years (SD = 6.7 years; range = 21-46 years). Results This form of the embedded figures task was much more difficult than the previous one. The mean number of figures completed in noise was 4.00 and in quiet 3,84. However, the noise effect failed to reach statistical significance (F < 1). Again, as a measure of the power of the experiment, a difference of .384 would have been significant; the standard deviation of individual differences in ability was 4.0079. The only effect to reach significance was the practice effect, F( 1,30) = 9.23,p = .005,3.31 figures being detected on the first run and 4.53 on the second. The noise did not interact with the size of the practice effect. In this experiment there was a zero correlation between age and the number of figures completed. Discussion The studies reported in this article support the growing literature that argues against explanation of noise effects in terms of changes in cue utilization to favor salient cues or a reduction in interference produced by a bias in attention always toward the more salient feature. Conceivably one could argue that the absence of an effect is due to the relatively low level of noise used or to the short duration of the noise exposure. However, effects of
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noise have been found with levels as low as 85 dB. (See Jones, Smith, & Broadbent, 1979; Smith, Note 2). Effects have also been found at very short exposure durations, and some of these have been explained in terms of attentional selectivity (e.g., Hockey & Hamilton, 1970). Thus a simplistic theory of noise effects, holding that selectivity of attention always changes in the same way in noise, should predict an effect in this study. Yet no effect was found. In practical situations, the main lesson of this study is to urge caution. One cannot assume that the effects of noise on a task of selecting relevant from irrelevant information will be beneficial; it depends on the particular task. Reference Notes 1. Broadbent, D. E. Low levels of noise and the naming of colors. Paper presented at the Third International Congress on Noise as a Public Health Problem, Freiburg, West Germany, 1978. 2. Smith, A. P. Low levels of noise and performance. Paper presented at the Third International Congress on Noise as a Public Health Problem, Freiburg, West Germany, 1978. References Arbuthnot, J. Cautionary note on the measurement of field independence. Perceptual and Motor Skills, 1972,55,479-488. Broadbent, D. E. Decision and stress. London: Academic Press, 1971.
Callaway, E. The influence of amobarbital (amylobarbitone) and methamphetamine on the focus of attention. Journal of Mental Science, 1959, 105, 382-392. Forster, P. M., & Grierson, A. Noise and attention selectivity: A reproducible phenomenon? British Journal of Psychology, 1978, 69, 489-498. Hartley, L. R., & Adams, J. Effects of noise on the Stroop test. Journal of Experimental Psychology, 1974, 102, 62-66. Hockey, G. R. J. Effect of loud noise on attentional selectivity. Quarterly Journal of Experimental Psychology, 1970, 22, 28-36. (a) Hockey, G. R. J. Signal probability and spatial location as possible bases for increased selectivity in noise. Quarterly Journal of Experimental Psychology, 1970, 22, 37-42. (b) Hockey, G. R. J., & Hamilton, P. Arousal and information selection in short-term memory. Nature (London), 1970,226, 866-867. Houston, B. K. Noise, task difficulty, and Stroop color-word performance. Journal of Experimental Psychology, 1969, 82, 403-404. Houston, B. K., & Jones, T. M. Distraction and Stroop color-word performance. Journal of Experimental Psychology, 1967, 74, 54-56. Jones, D. M., Smith, A. P., & Broadbent, D. E. Effects of moderate intensity noise on the Bakan vigilance task. Journal of Applied Psychology, 1979, 64, 627-634. Loeb, M., & Jones, P. D. Noise exposure, monitoring, and tracking performance as a function of signal bias and task priority. Ergonomics, 1978, 21, 265-277. Oilman, P. K. Field dependence and arousal. Perceptual and Motor Skills, 1964, 19, 441. Received February 22, 1979 •
