Human Factors: The Journal of the Human Factors and Ergonomics Society http://hfs.sagepub.com/
Conjoint Effect of Physical Stress and Noise Stress on Information Processing Performance and Cardiac Response Jay M. Finkelman, Lawrence R. Zeitlin, Richard A. Romoff, Michael A. Friend and Louis S. Brown Human Factors: The Journal of the Human Factors and Ergonomics Society 1979 21: 1 DOI: 10.1177/001872087902100101 The online version of this article can be found at: http://hfs.sagepub.com/content/21/1/1
Published by: http://www.sagepublications.com
On behalf of:
Human Factors and Ergonomics Society
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What is This?
HUMAN
F A C T O R S , 1979,21(1), 1-6
Conjoint Effect of Physical Stress and Noise Stress on Information Processing Performance and Cardiac Response JAY M. FINKELMAN', LAWRENCE R. ZEITLIN, RICHARD A. ROMOFF, MICHAEL A. FRIEND, aiid LOUIS S. BROWN, Bariicli College-The City Uiiiversity of New York
The coiijoiiit effectofphysicalstress, iiidciced by reqciiriiig siibjects to rim a treadmill, aiid 90 dB white iioise stress was evaluated 011 irifonnatioti processirig perforinarice iuiiig a delayed digit recall subsidiary task riteanire arid cardiac response. As anticipated, physical stress sigriificaittly raised lieart rate, aizd noise stress sigiiificaiitly degraded iiifoniiatioiz processing ability. The experititeitt failed to deiiioiistrate a liiiearly additive relatioiiship betweeti iioise aiid physical stress oii either cardiac respotise or iiifoniiatioii processifigperfoniiairce.
INTRODUCTION
crease in pulse rate. Davis, Buchwald, and Frankman (1955) reported that noise presented repeatedly at an intensity approaching the pain threshold (120-130 dB) caused a complex pattern of physiological reactions, which included an initial increase in volume pulse rate followed by a decrease to less than base level. Steinschneider, Lipton, and Richmond (1966) observed that, in the presence of white noise (presented at sequential levels of 55, 70, 85, and 100 dB), cardiac rate responses of one week old babies showed an increase in duration and a decrease in latency throughout the sequence. Gibson and Hall (1966) found that performance of mental tasks under noise conditions resulted in greate r heart acceleration than performance under no-noise conditions. Physical aiid iiieiital load. Lynch, Schuri, and D'Anna (1976) observed that moderate levels of static exercise (isometric muscle tension) caused significant initial increases in heart rate. Steele and Koons (1968), and Gib-
This investigation considers the impact of physical stress and noise stress on both information processing and cardiac response. It is well documented that physical stress increases heart rate and that noise stress degrades information processing ability. By exploring the remaining permutations and combinations of these variables in the research literature, two experimental questions pertaining to the possible additivity of the stressors can be posed. Faciors lVhicIi Affect Heart Rate Noise. Stewart (1970) considered noise a primary factor in well over 20 cardiovascular problems. Corso (1952) a n d Stamburgh (1950) found that exposure to high level, intermittent noise produced a significant in-
' Requests for reprints should be sent to Dr. Jay hi. Finkelman, Dean of Students, Baruch College, The City University of New York, 17 Lexington Avenue, New York, New York 10010. U.SA. @ 1979. The Human Factors Society, Inc.
1
All rights reserved.
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.
HUMAN
2-February, 1979
FACTORS
son and Hall (1966) reported that difficult mental tasks also increased mean heart rate and that this acceleration became more pronounced in a noisy environment (white noise at approximately 90 dB). Similarly, Boyce (1974) observed increases in heart rate for complex mental tasks and varying levels of physical stress. There is also some evidence to support the possibility of an interaction between noise conditions, task difficulty, and their effect upon heart rate (Costello and Hall, 1967).
Physical load. In addition t o t h e documented effect of noise on information processing ability, physical exertion may also influence mental task performance. Davey (1973) searched the literature pertaining to this question but did not find any evidence relating severe physical exertion to errors in mental performance. Davey's own investigation (1973), demonstrated that mental performance actually improves when it follows moderate dynamic physical exertion but deteriorates following severe physical exertion.
Factors lVIticli Affect Iiifonitatioii Processiirg Perfonitatice
Rationale for the Iirvestigation
Noise. Plutchik (1959) summarized the data by stating that performance impairments are more likely to occur during high intensity, intermittent sound than under lower intensity or steady sound, and the relative difficulty of the task is an important variable in determining the effect of noise on performance-the more difficult the task, the more likely it is that noise will be disruptive. Glass, Singer, and Friedman (1969) demonstrated that "unpredictable" noise (at either 110 dB or 56 dB) acted as a greater performance inhibitor than "predictable"' noise presented at the same level. Their results were consistent with those of Broadbent (1957) and Sanders (1961). Similarly, results of experiments reported by Horman and Osterkamp (1966), and Finkelman and Glass (1970) indicate that intermittent noise, as opposed to fixed-interval noise, inhibits information processing performance to a significant degree. Results of the former study were attributed to the disruptive effects of intermittent noise on logical and associative connections, (i.e., information or memory retrieval cues), while the latter investigation attributed the effect to the greater likelihood that unpredictable noise (in combination with multiple task performance) would overload an individual's channel capacity.
Noise, physical exertion, and information processing demands are all capable of increasing heart rate under certain conditions. Noise and high levels of physical exertion appear to interfere with information processing performance while moderate physical exertion may actually improve information processing under favorable conditions. The human factors specialist, aware that many industrial jobs combine information processing demands with physical demands while subjecting the worker to noise, may wish to know: (1) Is noise a potentiator of the effect of physical
stress in increasing heart rate? (2) Is physical stress a potentiator of the effect of noise in decreasing information processing performance?
In an effort to respond to these questions, the present experiment measures the conjoint effect of physical stress and noise on both information processing performance and cardiac response.
Subjects
METHOD
The subjects were 18 undergraduate students at Baruch College, nine male and nine female, ranging in age from 18 to 24.
Apparattis A Physiodyne clinical research treadmill
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February, 1979-3
JAY hl. FINKELMAN AND OTHERS
FEDCBA, BCDEFAIAFEDCB, CDEFAB/ BA FE DC, DE FAB C/CBA FE D , E FABC D/ DCBAFE, and FABCDWEDCBAF), for a total of 12 counterbalanced conditions per subject. A trial lasted 2 min with a 1-min interpolated rest between trials. Although the experimenters would have preferred a longer intertrial rest period in order to permit a return to base level heart rate, such a design would have precluded use of the volunteer student subjects due to time constraints imposed by the length of a single class session. However, it was felt that the partially counterbalanced design would help control for the carry-over effects of one condition to the next, although it is understood t h a t the results are attenuated to the extent of that carry-over.
system (Model 18-60), with automatic program control (Model 642) induced physical stress. Three tape recorders were employed, one for presentation of white noise through headphones, one for presentation of random digit sequences, and one for recording subjects' responses to the digits. The white noise was presented through a pair of Permoflex headphones (Model PDR-8) and was generated by a General Radio white noise generator (Model 1390-D). Noise levels were measured by a General Radio sound level meter (Model 1565-A), acoustically coupled to the headphones through a 6 cc coupler. A Physiodyne cardiotachometer (Model 609) presented heart rate totals for each trial period via digital display. An electronic digital clock was used to time each trial.
Iiideperrdeitt Variables The two independent variables, physical stress and noise stress, were operationalized as follows:
Procediire Physical stress was induced by requiring subjects to run a treadmill. Noise stress was induced by white noise presented through earphones. Subjects were tested in an internally controlled experimental design, undergoing all combinations of the physical stress (none, moderate, and high)/noise stress (none and moderate) conditions. A second task (delayed digit recall) was introduced to occupy the individual's "reserve" information processing capacity such that noise or physical stress would interfere with performance on that additional task. It was found to be appropriate for sensorimotor tasks and sensitive to noise stress in previous investigations (Finkelman and Glass, 1970; Zeitlin and Finkelman, 1975). Experiiiierrtal Desigiz Subjects were assigned to one of the six condition sequences on a random basis. Each subject ran a sequence of six conditions twice, serially and in reverse o r d e r (ABCDEFI
Physical stress.
.
None Subject remained stationary, in a standing position, for the entire trial. Moderate Subject ran on treadmill at 6.44 krdh/o" incline. High Subject ran on treadmill at 6.44 k d h l 20" incline.
All subjects were given a practice trial in which they ran on the treadmill a t 6.44 km/h/O" incline while presented with white noise. Noise stress. Subjects were asked if, to their knowledge, they possessed any hearing abnormalities. Only subjects reporting normal hearing were included in the experiment. Notze Subject wore headphones although no noise was presented, to insure experimental equivalence between conditions. Moderate Subject wore headphones and was presented with white noise at 90 dB for randomly ordered intervals of 3 s, 6 s, and 9 s, interspersed with randomly varied 3-s, 5-s, and 7-s silent periods.
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4-February, 1979
H'UMAN
FACTORS
Depertdertt Variables
noise a n d moderate-noise conditions. hloreover, the heart rate associated with Dependent measures were recorded in the moderate noise exceeded that associated with following manner: no noise for all but the no-physical stress Cardiac iizeasure. Three electrodes were condition although these differences were not wired to the cardiotachometer and approcollectively significant . priately positioned on the subjects so that the Although there is a consistent positive relatotal number of heart beats for the last 90 s of tionship between subsidiary task error scores the 2-min trial period was automatically reand physical stress levels for the no-noise corded. condition, the error scores for the moderateIiiforiitatioiz processing illeastire. The denoise condition show a decrease, from the layed digit recall task lasted the entire trial no-stress to moderate-physical stress condiperiod and entailed the subject's delayed reptions, followed by an increase in the high etition of digits presented randomly, one physical stress condition. The error scores asevery 2 s. The subject was instructed to repeat sociated with moderate noise significantly the numbers in a "one-digit-back" delay fashexceeded those associated with no noise for ion, as in the following example: all physical stress conditions. Tape presentation: An analysis of variance (ANOVA) for heart 9...3...1...7... rate as a function of noise stress and physical Subject's responses: stress revealed a significant difference in 9...3...1...7 mean heart rate between the three levels of physical stress (none: 3 = 75.8 bpm; moderThe digits were presented through ear3 = 82.0 bpm; high: 3 = 91 .O bpm), F (2, ate: phones, with the sound level adjusted so that 198) = 2 0 . 5 7 ,~ < 0.05. However, there was no each subject reported no difficulty in hearing significant difference in heart rate bet\veen the individual digits even during the highthe no-noise and moderate noise conditions, noise condition. Their verbal responses were and the interaction between noise stress and tape-recorded for subsequent analysis. The also not significant. physical stress was procedure is fully described in Zeitlin and An ANOVA for subsidiary task error scores Finkelman (1975). as a function of noise stress and physical stress revealed a significant difference in RESULTS mean error scores between the two levels of Table 1 shows a consistent positive effect of noise (no noise: = 2.12; moderate noise: 2 physical stress on heart rate for both the no- = 3.17), F (1,198) = 4.23.p < 0.05. However,
x
TABLE 1 hlean Heart Rate and SubsidiaryTask Errors for Two Levels of Noise and Three Levels of Physical Stress Subsidiary Task Errors Per Minute
Heart Beats Per Minute Physical Stress
None Moderate High
Mean
-
No Noise
Moderate Noise
No Noise
Moderate Noise
76.0 80.0 87.0 81 .O
75.5 84.0 94.0 84.5
1.70 2.00 2.65 2.12
3.10 2.90 3.50 3.17
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February, 1979- 5
JAY bl. FINKELMAN AND OTHERS
there was no significant difference in error scores among the three levels of physical stress, and the interaction between noise stress and physical stress was also not significant. DISCUSSION The results of this investigation reveal that physical stress has a significant effect upon heart rate but noise stress does not. They support the general observation that increased physical stress serves to stimulate heart rate, but do not significantly support the previously documented effect of noise stress on heart rate (Corso, 1952; Stamburgh, 1950). In a related failure to attain statistical significance, noise did not substantially potentiate the effect of physical stress on heart rate, although there was a trend in that direction. It is possible that the sound intensity of 90 dB in the moderate noise condition (versus 105 dB in Corso) was insufficient to produce the expected results in each instance. As anticipated, noise stress significantly degraded information processing performance, consistent with prior research (Finkelman and Glass, 1970; Boggs and Simon, 1968). Similar to the findings of Davey (1973). the present a u t h o r s observed a nonsignificant trend which suggested that information processing performance improved following “moderate” physical exertion but then deteriorated following “high” exertion. However, it must be noted that this nonsignificant relationship applied only to the moderate noise condition, whereas Davey observed a significant effect in the absence of noise. Perhaps even the high stress condition in the present study did not induce the level of physical exertion which Davey achieved in his moderate exertion condition, until noise stress was added to the system in the investigation. (Davey’s subjects pedalled a bicycle ergometer for a sufficient time to ensure an oxygen deficit.) It has already been dem-
onstrated that noise itself serves to interfere with information processing performance. Davey also documented tremendous variability in mental performance after a rnoderate (to high) physical exertion condition and concluded that intermediate exertion leads to different results in different subjects. This may help explain some of the inconsistencies in the research and the failure to attain significant differences in information processing performance as a function of physical stress. Davey explained the “inverted U” relationship between physical exertion a n d subsequent mental performance through the mechanism of arousal as proposed by Duffy (1962). Moderate arousal tends to facilitate mental performance while high arousal impairs it. The arousal model is also based upon the work of Freeman (1948), Lindsley (1951), Hebb (1955), and Malmo (1959). In the present study there were only minor and inconsistent differences in the number of subsidiary task errors under the three conditions of physical stress with moderate noise. However, under no noise, there appeared to be greater differences between subsidiary task errors under the different load conditions. This suggests that information processing loads such as those induced by noise and physical stress may not be entirely additive o r linear. Broadbent (1971) comments that if two stressors impair performance by affecting different mechanisms, the effect of each stressor should be independent and additive. If, on the other hand, both stressors influence the same mechanism, the result may be even more drastic than the combined effect. However, Wilkinson (1963) notes that the opposite may occur where the impact of two stressors in combination may be much less than the sum of their individual effects as they oppose each other’s effects at various levels. In conclusion, these data relate to the two experimental questions posed at the onset as follows:
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6-February, 1979
HUMAN
(1)A moderate level of noise appeared to be a slight, and admittedly nonsignificant, potentiator of the effect of physical stress on heart rate. It is possible that the outcome would have been more conclusive with a higher level of noise. (2) Physical stress had a n inconsistent and nonsignificant influence on the effect of noise on information processing performance. It is also possible that modcrate physical stress may even facilitate information processing pcrformance, although in the present study this nonsignificant trend only emerged under the noise condition.
ACKNOWLEDGMENT The investigation was supported. in part. by a grant from The City University of New York Faculty Research Award Program.
REFERENCES Boggs, D. H. and Simon, J. R. Differential effects of noise on tasks of varying complexity. Journal of Applied Psychology, 1968.52. 148-153. Broadbent, D. E. Effects of noise on behavior. In C. Al. Harris (Ed.) Handbook o f noise control. New York: hfcCraw-Hill, 1957. Broadbent, D. E. Decisioiz and srress. New York: Academic Press, 1971. Corso. J. F. The effects of noise on human behavior. Wright-Patterson AFB, Ohio: Wright A i r Development Center, WADCTechnical Report, No. 53-81, 1952. Cited by R. Plutchik, The effects of high intensity intermittent sound on performance, feeling. and physiology. Psyrho~ogicafBillletin, 1959.56. 133-15 I. Costello. C. C. and Hall. hl. Heart rates during performance of a mental task under noise conditions. ~syChorzo~nic Scietice, 1967.8, 405-406. Davey, C. P. Physical exertion and mental performance. Ergoiiomics, 1973.16, 595-599. Davis. R. C.. Buchwald. A. hf.. and Frankman, R. \V. Autonomic and muscular responses and their relationship to simple stimuli. Psycliological Afo~iographs, 1955.69. 1-71.
Duffy. E. Aciicwtiorz aiid behavior. New York: \Viley. 1962. Finkelman, J. Al. and Class, D. C. Reappraisal of the relationship between noise and human performance by means of a subsidiary task mensurr.Joiinza[ofApplied PSJChOfOW', 1970.53, 21 1-213.
FACTORS
Freeman. C. L. The energerics ofhiirnati behavior. Ithaca. N.Y.: Cornell University Press, 1918. Gibson, D. and Hall. hl. K. Cardiovascular change and mental task gradient. Psycho~ioniicScience, 1966, 6, 245-246.
Glass, D. C., Singer, J. E., and Friedman, L. N. Psychic cost of adaptation to a n environmental stressor.Jozinia1 of Personality and Social Psycliologv, 1969.12, 200-2 10. Hebb. D. 0. Drives and C.N.S. (conceptual nervous system). Psycliological Review, 3955.62. 243-254. Horman. H. a n d Osterkamp, U. On the influence of intermittent noise upon the organization of memory. Zeitschriff fiir Experi~nenrollc rind Aiigeicandte Psychologie. 1966,13, 265-273. (Psychological Abstracts. 1966).
Linds1ey.D. B.Emotion.In S.S.Stevens(Ed.)Handbookof erperiineiital ps~c1zology.New York: Wiley, 1951, Lynch, C. W.,Schuri. U..and D'Anna. J. Effects of isometric muscle tension on vasomotor activity and heart ra t e. Ps~chopliysiololy,1976.13, 222-229. hlalmo. R. B.Activation: A neuropsychological dimension. Psychological Review. 1939.66, 367-386. Plutchik, R. The effects of high intensity intermittent sound o n performance, feeling, and physiology. Psychofogical Biillerbz. 1959,56. 133-151. Sanders, A. F.The influence of noise on two discrimination tasks. Ergotzonrics, 1961,4, 253-258. Stamburgh. C. J. An investigation of certain individual differences under the stress of high intensity sound. Unpublished doctoral dissertation, Pennsylvania State College, 1950. Cited by R. Plutchik. The effects of high intensity intermittent sound on performance. feeling, and physiology. Psychological Biillerirz, 1959. 56. 133151.
Steele. W. C. and Koons, Jr., P. B. Cardiac response to mental arithmetic under quiet and white noise distraction. Psycltonomic Science, 1968. I I . 273-274. Steinschneider, A.. Lipton. E. L.. and Richmond, J. B: Auditory sensitivity in the infant: Effect of intensity on cardiac a n d motor responsirity. Child Developnient, '
1966.37, 233.252.
Stewart. \V. Cited by A. B. Baron.The tyramy ofnoise. New York: St. hlartin's Press, 1970. Wilkinson. R. T. Interaction of noise with knowledge of results and sleep deprivation. Journal of€xperimerztal PS~ChObgy,1963.66. 332-337. Zeitlin. L. R. and Finkelman. J. A l . hfeasurement of operator loading in pursuit rotor tracking by a "random digit" generation subsidiary task. Stevens Instit u t e of Technology. Hoboken. N. J.: Daridson Laboratory Report No. 1401. August, 1969. Zeitlin, L. R. and Finkelman. J. hl. Research note: Subsidiary task techniques of digit generation and digit recall as indirect measures of operator 1oading.Hiiniaiz Factors, 1975, 17, 2 18-220.
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Conjoint Effect of Physical Stress and Noise Stress on Information Processing Performance and Cardiac Response Jay M. Finkelman, Lawrence R. Zeitlin, Richard A. Romoff, Michael A. Friend and Louis S. Brown Human Factors: The Journal of the Human Factors and Ergonomics Society 1979 21: 1 DOI: 10.1177/001872087902100101 The online version of this article can be found at: http://hfs.sagepub.com/content/21/1/1
Published by: http://www.sagepublications.com
On behalf of:
Human Factors and Ergonomics Society
Additional services and information for Human Factors: The Journal of the Human Factors and Ergonomics Society can be found at: Email Alerts: http://hfs.sagepub.com/cgi/alerts Subscriptions: http://hfs.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations: http://hfs.sagepub.com/content/21/1/1.refs.html
>> Version of Record - Feb 1, 1979 Downloaded from hfs.sagepub.com at NORTHERN ILLINOIS UNIV on September 4, 2014
What is This?
HUMAN
F A C T O R S , 1979,21(1), 1-6
Conjoint Effect of Physical Stress and Noise Stress on Information Processing Performance and Cardiac Response JAY M. FINKELMAN', LAWRENCE R. ZEITLIN, RICHARD A. ROMOFF, MICHAEL A. FRIEND, aiid LOUIS S. BROWN, Bariicli College-The City Uiiiversity of New York
The coiijoiiit effectofphysicalstress, iiidciced by reqciiriiig siibjects to rim a treadmill, aiid 90 dB white iioise stress was evaluated 011 irifonnatioti processirig perforinarice iuiiig a delayed digit recall subsidiary task riteanire arid cardiac response. As anticipated, physical stress sigriificaittly raised lieart rate, aizd noise stress sigiiificaiitly degraded iiifoniiatioiz processing ability. The experititeitt failed to deiiioiistrate a liiiearly additive relatioiiship betweeti iioise aiid physical stress oii either cardiac respotise or iiifoniiatioii processifigperfoniiairce.
INTRODUCTION
crease in pulse rate. Davis, Buchwald, and Frankman (1955) reported that noise presented repeatedly at an intensity approaching the pain threshold (120-130 dB) caused a complex pattern of physiological reactions, which included an initial increase in volume pulse rate followed by a decrease to less than base level. Steinschneider, Lipton, and Richmond (1966) observed that, in the presence of white noise (presented at sequential levels of 55, 70, 85, and 100 dB), cardiac rate responses of one week old babies showed an increase in duration and a decrease in latency throughout the sequence. Gibson and Hall (1966) found that performance of mental tasks under noise conditions resulted in greate r heart acceleration than performance under no-noise conditions. Physical aiid iiieiital load. Lynch, Schuri, and D'Anna (1976) observed that moderate levels of static exercise (isometric muscle tension) caused significant initial increases in heart rate. Steele and Koons (1968), and Gib-
This investigation considers the impact of physical stress and noise stress on both information processing and cardiac response. It is well documented that physical stress increases heart rate and that noise stress degrades information processing ability. By exploring the remaining permutations and combinations of these variables in the research literature, two experimental questions pertaining to the possible additivity of the stressors can be posed. Faciors lVhicIi Affect Heart Rate Noise. Stewart (1970) considered noise a primary factor in well over 20 cardiovascular problems. Corso (1952) a n d Stamburgh (1950) found that exposure to high level, intermittent noise produced a significant in-
' Requests for reprints should be sent to Dr. Jay hi. Finkelman, Dean of Students, Baruch College, The City University of New York, 17 Lexington Avenue, New York, New York 10010. U.SA. @ 1979. The Human Factors Society, Inc.
1
All rights reserved.
Downloaded from hfs.sagepub.com at NORTHERN ILLINOIS UNIV on September 4, 2014
.
HUMAN
2-February, 1979
FACTORS
son and Hall (1966) reported that difficult mental tasks also increased mean heart rate and that this acceleration became more pronounced in a noisy environment (white noise at approximately 90 dB). Similarly, Boyce (1974) observed increases in heart rate for complex mental tasks and varying levels of physical stress. There is also some evidence to support the possibility of an interaction between noise conditions, task difficulty, and their effect upon heart rate (Costello and Hall, 1967).
Physical load. In addition t o t h e documented effect of noise on information processing ability, physical exertion may also influence mental task performance. Davey (1973) searched the literature pertaining to this question but did not find any evidence relating severe physical exertion to errors in mental performance. Davey's own investigation (1973), demonstrated that mental performance actually improves when it follows moderate dynamic physical exertion but deteriorates following severe physical exertion.
Factors lVIticli Affect Iiifonitatioii Processiirg Perfonitatice
Rationale for the Iirvestigation
Noise. Plutchik (1959) summarized the data by stating that performance impairments are more likely to occur during high intensity, intermittent sound than under lower intensity or steady sound, and the relative difficulty of the task is an important variable in determining the effect of noise on performance-the more difficult the task, the more likely it is that noise will be disruptive. Glass, Singer, and Friedman (1969) demonstrated that "unpredictable" noise (at either 110 dB or 56 dB) acted as a greater performance inhibitor than "predictable"' noise presented at the same level. Their results were consistent with those of Broadbent (1957) and Sanders (1961). Similarly, results of experiments reported by Horman and Osterkamp (1966), and Finkelman and Glass (1970) indicate that intermittent noise, as opposed to fixed-interval noise, inhibits information processing performance to a significant degree. Results of the former study were attributed to the disruptive effects of intermittent noise on logical and associative connections, (i.e., information or memory retrieval cues), while the latter investigation attributed the effect to the greater likelihood that unpredictable noise (in combination with multiple task performance) would overload an individual's channel capacity.
Noise, physical exertion, and information processing demands are all capable of increasing heart rate under certain conditions. Noise and high levels of physical exertion appear to interfere with information processing performance while moderate physical exertion may actually improve information processing under favorable conditions. The human factors specialist, aware that many industrial jobs combine information processing demands with physical demands while subjecting the worker to noise, may wish to know: (1) Is noise a potentiator of the effect of physical
stress in increasing heart rate? (2) Is physical stress a potentiator of the effect of noise in decreasing information processing performance?
In an effort to respond to these questions, the present experiment measures the conjoint effect of physical stress and noise on both information processing performance and cardiac response.
Subjects
METHOD
The subjects were 18 undergraduate students at Baruch College, nine male and nine female, ranging in age from 18 to 24.
Apparattis A Physiodyne clinical research treadmill
Downloaded from hfs.sagepub.com at NORTHERN ILLINOIS UNIV on September 4, 2014
February, 1979-3
JAY hl. FINKELMAN AND OTHERS
FEDCBA, BCDEFAIAFEDCB, CDEFAB/ BA FE DC, DE FAB C/CBA FE D , E FABC D/ DCBAFE, and FABCDWEDCBAF), for a total of 12 counterbalanced conditions per subject. A trial lasted 2 min with a 1-min interpolated rest between trials. Although the experimenters would have preferred a longer intertrial rest period in order to permit a return to base level heart rate, such a design would have precluded use of the volunteer student subjects due to time constraints imposed by the length of a single class session. However, it was felt that the partially counterbalanced design would help control for the carry-over effects of one condition to the next, although it is understood t h a t the results are attenuated to the extent of that carry-over.
system (Model 18-60), with automatic program control (Model 642) induced physical stress. Three tape recorders were employed, one for presentation of white noise through headphones, one for presentation of random digit sequences, and one for recording subjects' responses to the digits. The white noise was presented through a pair of Permoflex headphones (Model PDR-8) and was generated by a General Radio white noise generator (Model 1390-D). Noise levels were measured by a General Radio sound level meter (Model 1565-A), acoustically coupled to the headphones through a 6 cc coupler. A Physiodyne cardiotachometer (Model 609) presented heart rate totals for each trial period via digital display. An electronic digital clock was used to time each trial.
Iiideperrdeitt Variables The two independent variables, physical stress and noise stress, were operationalized as follows:
Procediire Physical stress was induced by requiring subjects to run a treadmill. Noise stress was induced by white noise presented through earphones. Subjects were tested in an internally controlled experimental design, undergoing all combinations of the physical stress (none, moderate, and high)/noise stress (none and moderate) conditions. A second task (delayed digit recall) was introduced to occupy the individual's "reserve" information processing capacity such that noise or physical stress would interfere with performance on that additional task. It was found to be appropriate for sensorimotor tasks and sensitive to noise stress in previous investigations (Finkelman and Glass, 1970; Zeitlin and Finkelman, 1975). Experiiiierrtal Desigiz Subjects were assigned to one of the six condition sequences on a random basis. Each subject ran a sequence of six conditions twice, serially and in reverse o r d e r (ABCDEFI
Physical stress.
.
None Subject remained stationary, in a standing position, for the entire trial. Moderate Subject ran on treadmill at 6.44 krdh/o" incline. High Subject ran on treadmill at 6.44 k d h l 20" incline.
All subjects were given a practice trial in which they ran on the treadmill a t 6.44 km/h/O" incline while presented with white noise. Noise stress. Subjects were asked if, to their knowledge, they possessed any hearing abnormalities. Only subjects reporting normal hearing were included in the experiment. Notze Subject wore headphones although no noise was presented, to insure experimental equivalence between conditions. Moderate Subject wore headphones and was presented with white noise at 90 dB for randomly ordered intervals of 3 s, 6 s, and 9 s, interspersed with randomly varied 3-s, 5-s, and 7-s silent periods.
Downloaded from hfs.sagepub.com at NORTHERN ILLINOIS UNIV on September 4, 2014
4-February, 1979
H'UMAN
FACTORS
Depertdertt Variables
noise a n d moderate-noise conditions. hloreover, the heart rate associated with Dependent measures were recorded in the moderate noise exceeded that associated with following manner: no noise for all but the no-physical stress Cardiac iizeasure. Three electrodes were condition although these differences were not wired to the cardiotachometer and approcollectively significant . priately positioned on the subjects so that the Although there is a consistent positive relatotal number of heart beats for the last 90 s of tionship between subsidiary task error scores the 2-min trial period was automatically reand physical stress levels for the no-noise corded. condition, the error scores for the moderateIiiforiitatioiz processing illeastire. The denoise condition show a decrease, from the layed digit recall task lasted the entire trial no-stress to moderate-physical stress condiperiod and entailed the subject's delayed reptions, followed by an increase in the high etition of digits presented randomly, one physical stress condition. The error scores asevery 2 s. The subject was instructed to repeat sociated with moderate noise significantly the numbers in a "one-digit-back" delay fashexceeded those associated with no noise for ion, as in the following example: all physical stress conditions. Tape presentation: An analysis of variance (ANOVA) for heart 9...3...1...7... rate as a function of noise stress and physical Subject's responses: stress revealed a significant difference in 9...3...1...7 mean heart rate between the three levels of physical stress (none: 3 = 75.8 bpm; moderThe digits were presented through ear3 = 82.0 bpm; high: 3 = 91 .O bpm), F (2, ate: phones, with the sound level adjusted so that 198) = 2 0 . 5 7 ,~ < 0.05. However, there was no each subject reported no difficulty in hearing significant difference in heart rate bet\veen the individual digits even during the highthe no-noise and moderate noise conditions, noise condition. Their verbal responses were and the interaction between noise stress and tape-recorded for subsequent analysis. The also not significant. physical stress was procedure is fully described in Zeitlin and An ANOVA for subsidiary task error scores Finkelman (1975). as a function of noise stress and physical stress revealed a significant difference in RESULTS mean error scores between the two levels of Table 1 shows a consistent positive effect of noise (no noise: = 2.12; moderate noise: 2 physical stress on heart rate for both the no- = 3.17), F (1,198) = 4.23.p < 0.05. However,
x
TABLE 1 hlean Heart Rate and SubsidiaryTask Errors for Two Levels of Noise and Three Levels of Physical Stress Subsidiary Task Errors Per Minute
Heart Beats Per Minute Physical Stress
None Moderate High
Mean
-
No Noise
Moderate Noise
No Noise
Moderate Noise
76.0 80.0 87.0 81 .O
75.5 84.0 94.0 84.5
1.70 2.00 2.65 2.12
3.10 2.90 3.50 3.17
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February, 1979- 5
JAY bl. FINKELMAN AND OTHERS
there was no significant difference in error scores among the three levels of physical stress, and the interaction between noise stress and physical stress was also not significant. DISCUSSION The results of this investigation reveal that physical stress has a significant effect upon heart rate but noise stress does not. They support the general observation that increased physical stress serves to stimulate heart rate, but do not significantly support the previously documented effect of noise stress on heart rate (Corso, 1952; Stamburgh, 1950). In a related failure to attain statistical significance, noise did not substantially potentiate the effect of physical stress on heart rate, although there was a trend in that direction. It is possible that the sound intensity of 90 dB in the moderate noise condition (versus 105 dB in Corso) was insufficient to produce the expected results in each instance. As anticipated, noise stress significantly degraded information processing performance, consistent with prior research (Finkelman and Glass, 1970; Boggs and Simon, 1968). Similar to the findings of Davey (1973). the present a u t h o r s observed a nonsignificant trend which suggested that information processing performance improved following “moderate” physical exertion but then deteriorated following “high” exertion. However, it must be noted that this nonsignificant relationship applied only to the moderate noise condition, whereas Davey observed a significant effect in the absence of noise. Perhaps even the high stress condition in the present study did not induce the level of physical exertion which Davey achieved in his moderate exertion condition, until noise stress was added to the system in the investigation. (Davey’s subjects pedalled a bicycle ergometer for a sufficient time to ensure an oxygen deficit.) It has already been dem-
onstrated that noise itself serves to interfere with information processing performance. Davey also documented tremendous variability in mental performance after a rnoderate (to high) physical exertion condition and concluded that intermediate exertion leads to different results in different subjects. This may help explain some of the inconsistencies in the research and the failure to attain significant differences in information processing performance as a function of physical stress. Davey explained the “inverted U” relationship between physical exertion a n d subsequent mental performance through the mechanism of arousal as proposed by Duffy (1962). Moderate arousal tends to facilitate mental performance while high arousal impairs it. The arousal model is also based upon the work of Freeman (1948), Lindsley (1951), Hebb (1955), and Malmo (1959). In the present study there were only minor and inconsistent differences in the number of subsidiary task errors under the three conditions of physical stress with moderate noise. However, under no noise, there appeared to be greater differences between subsidiary task errors under the different load conditions. This suggests that information processing loads such as those induced by noise and physical stress may not be entirely additive o r linear. Broadbent (1971) comments that if two stressors impair performance by affecting different mechanisms, the effect of each stressor should be independent and additive. If, on the other hand, both stressors influence the same mechanism, the result may be even more drastic than the combined effect. However, Wilkinson (1963) notes that the opposite may occur where the impact of two stressors in combination may be much less than the sum of their individual effects as they oppose each other’s effects at various levels. In conclusion, these data relate to the two experimental questions posed at the onset as follows:
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6-February, 1979
HUMAN
(1)A moderate level of noise appeared to be a slight, and admittedly nonsignificant, potentiator of the effect of physical stress on heart rate. It is possible that the outcome would have been more conclusive with a higher level of noise. (2) Physical stress had a n inconsistent and nonsignificant influence on the effect of noise on information processing performance. It is also possible that modcrate physical stress may even facilitate information processing pcrformance, although in the present study this nonsignificant trend only emerged under the noise condition.
ACKNOWLEDGMENT The investigation was supported. in part. by a grant from The City University of New York Faculty Research Award Program.
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Duffy. E. Aciicwtiorz aiid behavior. New York: \Viley. 1962. Finkelman, J. Al. and Class, D. C. Reappraisal of the relationship between noise and human performance by means of a subsidiary task mensurr.Joiinza[ofApplied PSJChOfOW', 1970.53, 21 1-213.
FACTORS
Freeman. C. L. The energerics ofhiirnati behavior. Ithaca. N.Y.: Cornell University Press, 1918. Gibson, D. and Hall. hl. K. Cardiovascular change and mental task gradient. Psycho~ioniicScience, 1966, 6, 245-246.
Glass, D. C., Singer, J. E., and Friedman, L. N. Psychic cost of adaptation to a n environmental stressor.Jozinia1 of Personality and Social Psycliologv, 1969.12, 200-2 10. Hebb. D. 0. Drives and C.N.S. (conceptual nervous system). Psycliological Review, 3955.62. 243-254. Horman. H. a n d Osterkamp, U. On the influence of intermittent noise upon the organization of memory. Zeitschriff fiir Experi~nenrollc rind Aiigeicandte Psychologie. 1966,13, 265-273. (Psychological Abstracts. 1966).
Linds1ey.D. B.Emotion.In S.S.Stevens(Ed.)Handbookof erperiineiital ps~c1zology.New York: Wiley, 1951, Lynch, C. W.,Schuri. U..and D'Anna. J. Effects of isometric muscle tension on vasomotor activity and heart ra t e. Ps~chopliysiololy,1976.13, 222-229. hlalmo. R. B.Activation: A neuropsychological dimension. Psychological Review. 1939.66, 367-386. Plutchik, R. The effects of high intensity intermittent sound o n performance, feeling, and physiology. Psychofogical Biillerbz. 1959,56. 133-151. Sanders, A. F.The influence of noise on two discrimination tasks. Ergotzonrics, 1961,4, 253-258. Stamburgh. C. J. An investigation of certain individual differences under the stress of high intensity sound. Unpublished doctoral dissertation, Pennsylvania State College, 1950. Cited by R. Plutchik. The effects of high intensity intermittent sound on performance. feeling, and physiology. Psychological Biillerirz, 1959. 56. 133151.
Steele. W. C. and Koons, Jr., P. B. Cardiac response to mental arithmetic under quiet and white noise distraction. Psycltonomic Science, 1968. I I . 273-274. Steinschneider, A.. Lipton. E. L.. and Richmond, J. B: Auditory sensitivity in the infant: Effect of intensity on cardiac a n d motor responsirity. Child Developnient, '
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Stewart. \V. Cited by A. B. Baron.The tyramy ofnoise. New York: St. hlartin's Press, 1970. Wilkinson. R. T. Interaction of noise with knowledge of results and sleep deprivation. Journal of€xperimerztal PS~ChObgy,1963.66. 332-337. Zeitlin. L. R. and Finkelman. J. A l . hfeasurement of operator loading in pursuit rotor tracking by a "random digit" generation subsidiary task. Stevens Instit u t e of Technology. Hoboken. N. J.: Daridson Laboratory Report No. 1401. August, 1969. Zeitlin, L. R. and Finkelman. J. hl. Research note: Subsidiary task techniques of digit generation and digit recall as indirect measures of operator 1oading.Hiiniaiz Factors, 1975, 17, 2 18-220.
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