Perceptual and Motor Skills, 1979.49, 851-857. @ Perceptual and Motor Skills 1979
TIME-VARIED NOISE EFFECTS O N COLOR-WORD TEST PERFORMANCE1 GEORGE D. OGDEN3 A N D ANGELA M. RIECK University of Maryland G L Y N N D. COATES Old Dominion University Summary.-The effects of continuous and time-varied 85 dBA broadband noise o n the performance of a Stroop-type color-word test and a related word. reading task were investigated. 10 subjects served in one of three groups receiving either continuous, periodic, o r aperiodic noise. All subjects performed in both low noise ( 6 5 dBA) and high noise ( 8 5 dBA) conditions on 80 trials of both word reading and color naming. Median reaction times in the word-reading task were unaffected by either noise intensity or the timevaried aspects of the noise. However, median reaction times in the colornaming task were significantly elevated in the 85-dBA noise condition. Also, reaction times in the high aperiodic noise condition were significantly elevated relative to rhe continuous and periodic noise conditions. Results are discussed within the framework of arousal, filter, and information theories.
In 1935 Stroop reported that response times to stimuli, hues written in incongruent color names, were much longer than response times to hue patches. Since that time, the task involving these stimuli, known as the Stroop colorword test, has been reported to be sensitive to various stressors, and this sensitivity has been attributed to the attentional demands of the task. Several investigators have examined the effects of auditory noise on Stroop test performance, but the reported effects of noise have been inconsistent. For example, Hartley and Adams (1974) reported that, althoagh noise had an initial positive effect on Stroop performance, there was a significant detrimental effect on performance during the final 10 min. of a 30-min. session. Other investigators have reported that noise clearly improves performance (O'Malley & Poplawsky, 1971). Houston and Jones (1967) exposed their subjects to 75 dBA of "jibberish" and found that requiring the subjeccs to ignore the noise improved their performance. The conflicting reports of the effects of auditory noise on performance is not, however, restricted to the Scroop task as investigators of the effects of noise on other performances have also reported contradictory results. Noise sometimes improves task performance (Kirk & Hecht, 1963), noise sometimes detrimentally affects performance ( Weinstein, 1974), and quite often, noise 'Supported in part by the National Aeronautics and Space Administration under Research Grant No. NSG-1092, "A Review and Preliminary Evaluation of Methodological Factors in Performance Assessments of Time-varying Aircraft Noise Effects." "eprints may be obtained from George D. Ogden, Department of Psychology, University o f Maryland, College Park, Maryland 20742.
852
G. D. OGDEN. ET AL.
has no effect on performance. Thus, it is noc surprising that noise effects on Stroop performance appear ambiguous, for this accurately reflects the present state of the literature on effects of noise. It should be noted, however, that in the previously described Stroop test experiments, methodological differences, rather than the ambiguous state of noise effects, may account for the divergent results. A wide variety of colorword test forms have been used as well as a wide variety of dependent measures. For example, Hartley and Adams (1974) used a checklist that required subjects to check the correct answer; O'Malley and Poplawsky (1971) and Houston and Jones (1967), on the ocher hand, used verbal responses. Although most of the studies employed total time to completion for all responses as the major dependent variable, Hartley and Adams reported a difference score representing the difference between total time for Stroop color naming and total time for regular color naming. The other source of methodological differences which might account for differences in results concerns the type of noise used. For example, in addition to differences in frequency or intensity of noise, noise can be varied along a temporal dimension. Time-varied noise can be continuous (with little or no variation), periodic (with predictable variations in onset and offset), or aperiodic (with random or unpredictable variations in onset and offset). A number of investigators have manipulated these time-varied aspects. For example, Warner and Heimstra (1972) found that performance on a visual search task improved with the introduction of periodic noise as compared to continuous noise. Finkleman and Glass (1970) found that unpredictable (aperiodic) noise had a detrimental effect on performance when compared to periodic noise in a dual-task performance setting. The purpose of the present st~ldywas to decermine the effects of auditory noise on the performance of a Stroop-type color-word test and a related wordreading task. To assess the effects of the temporal characteristics of the noise as well as the effects of the intensiry level, both aspects of the noise were systematically varied. Further, to maximize the precision of measurement of any possible effects, reaction time to discrete trials was employed as the primary dependent measure.
METHOD The experimental design involved the manipulation of three factors. The first factor was task type, i.e., color naming and word reading; the second faccor was noise level, i.e., low and h ~ g h Subjects performed in all four of these conditions. In the conditions of high noise level, one-third of the subjects were assigned to one of the three subconditions of continuous, periodic, or aperiodic noise. The design was counterbalanced For both order of task and of noise level.
NOISE EFFECTS ON STROOP TEST
853
Subjects were 30 students at Old Dominion University. The sample included 22 females and 8 males; the median age was 21 yr. Subjects were randomly assigned to the temporal subconditions of the high noise level with the stipulation that there would be an approximately equal ratio of males to females in each condition. All subjects had normal hearing and exhibited no color blindness or other visual deficiencies.
Stimuli The stimuli were 80 35-mm slides photographed using Kodachrome-25 film under photolamps (3500' K ) wich a Wratten 80B filter. The stimulus materials were constructed from highly saturated posterboard which provided both lettering and background. The stimuli were constructed wich five hues of letters, i.e., red, blue, green, yellow, and white, that spelled four words, i.e., red, blue, green, and yellow, on Five background colors, i.e., red, blue, green, yellow, and white. The letters, words, and backgrounds were combined factorially, excluding those cases in which the hues of the letters were identical to the hue of the background, to provide the stimulus population. Eqz~ipment The slides were back-projected onto a rear-projection screen and presented at eye level approximately 1 m from the subject. The stimulus presentation duration (750 m m . ) was controlled by a Wollensak shutter (Device 4 H 4 ) . Stimulus presentation activated a Hunter photoelectric cell (Model 31 ) which closed a photoelectric relay (Hunter Model 335s) and started a Hunter digital timer (Model 1521). The timer was stopped by a verbal response into a lnicrophone mounted in front of the subject. A light mounted at the bottom of the rear-projection screen was illuminated briefly approximately 1 sec. prior to stimulus presentation and sewed as a warning signal.
Noise Broadband white noise presented by means of headphones was used for all conditions. The sound pressure level measured at the subject's ear was 65 dBA for the conditions of low noise level. In the condition of high continuous noise, the noise level was set at 85 dBA. Noise in the condition of high periodic noise had an on-off ratio of 50:50 with the "on" intensity at 85 dBA and the "off" intensity at 65 dBA with a complete cycle occurring each second. In the condition with high aperiodic noise, each 1 sec. of noise was selected randomly with equal probabilities from three 1-sec. cycles: ( a ) .25 sec. at 65 dBA and .75 sec. at 85 dBA, ( b ) .5 sec. at 65 dBA and .5 sec. at 85 dBA, and ( c ) .75 sec. at 65 dBA and .25 sec. at 85 dBA. The noise was produced by a white-noise generator (Lahyette Model 1431) and a series of industrial timers and relays were employed to produce
854
G. D. OGDEN, ET AL.
the effects of periodic and aperiodic noise which were recorded on separate reel-to-reel audio tapes. Sound levels were measured at the level of the subject's ear in the headphones, and sound levels were calibrated for each subject in each condition. At the beginning of the experiment, subjeccs were given an audiogram. Normal hearing was defined as having no greater than a 15-dB hearing loss in either ear at any frequency between 500 Hz and 4000 Hz. If the subject demonstrated normal hearing, the experiment proceeded. Each subject participated in two sessions, one session under conditions of Low noise and one session under the High noise condition to which he was assigned; the order in which the subject received the Low and High noise conditions was counterbalanced. Subjects were instrucced as to the nature of their tasks and were given a demonstration of the stimuli and the warning light. In the color-word test, subjects were instructed to respond by giving the color of the letters in the slide. In the word-reading task, subjeccs were instructed co respond by reading the word in the slide. Subjects were instructed to respond as rapidly as possible but not to make any more than two errors in a session. In each session 160 slides were presented, 80 for the word-reading task and 80 for the color-naming task. The order of the tasks was also counterbalanced. There was a 5-min. break between the two sessions, during which the subject was allowed to leave the experimental room. Each session required approximately 30 min. At the completion of the experiment, the subject was tested again for any possible hearing loss that may have occurred from the noise exposure in the experiment; if no threshold shift was evident, the subject was released. The entire experiment lasted approximately 75 min.
RESULTS The primary dependent measure was the median reaction time of the 80 trials of each task. Errors were also recorded, but since the instructions stressed accuracy, very few errors resulted. A total of 56 errors were recorded in the color-naming task (4% of the 12,800 trials), and only 1 error in the wordreading task. Of the 57 errors, 33 occurred under the high-noise conditions and 24 under the low-noise conditions. The efficacy of the experimental counterbalancing of noise order and task order was analyzed. The results of these analyses indicated that neither noise order nor task order had a significant effect on median RT; nor did any of these order effects interact with the experimental factors. The word-reading task and the color-naming task were analyzed separately due to the different task demands and the highly distinctive distributions of
NOlSE EFFECTS ON STROOP TEST
855
RT. The mean of median R T in the word-reading task was 501 msec. (SD = 47.4 msec.) while the mean of the median R T in the color-naming task was 664 msec. (SD = 48.1 msec.).
Word-reading Performances Median R T in the word-reading task were analyzed with a two-factor analysis of variance, with factors of Noise Level (Low and High) and Temporal Condition ( Continuous, Periodic, and Aperiodic). There were no significant main effects due to the level of noise, temporal conditions, nor the interaction of the two factors. Color-naming Performances The analysis of median R T in the color-naming task also employed a twofactor analysis of variance to determine the effects of noise level in each of the three noise conditions. Reliable differences were obtained between the Low Noise and High Noise levels (F1," T 5.27, p < .05). The general effect of the higher noise intensity was to increase RT (or degrade color-naming performance). The mean of median R T in the Low-noise conditions was 655 msec., with a standard deviation of 41.7 msec., and the mean of median R T in the High-noise conditions was 673 msec., with a standard deviation of 53.8 msec. The nature of the noise-level effect was tested for each Temporal condition by means of linear contrasts of the Noise Level X Temporal Condition interaction which was significant (F3,37 = 5.22, p < .01). The average increase in R T between the Low and High noise levels in the continuous and periodic groups was 16 msec. and 25 msec., respectively. These differences were not statistically reliable. However, the increase in R T between the Low and High noise levels in the aperiodic group was 48 msec. This difference was reliable (tls = 2.27, p < .05).
DISCUSSION Theoretical formulations of noise effects on Stroop color-naming are generally of three types. One explanation concerns the arousal theories or the arousal-attention hypothesis, whereby the performance effects due to noise are caused by its activating or arousing properties (cf. Broadbent, 1957). Presumably, arousal narrows attention and, thereby, helps or hinders performance depending on whether the information being filtered is relevant to performance. The present results are consistent with this explanation only to the extent that the level of arousal or activation can be shown to be a function of the timevaried properties of the noise. Selective filter or distraction models (Treisman, 1969) assume that noise affects the perceptual system. The selective filter determines the informational input in the system-which ideally in the Stroop task, would focus on the
856
G. D. OGDEN, ET AL.
color and filter the word. Further, noise that is relevant, intense, or novel may be input into the system causing perceptual inefficiency in filtering "irrelevant" information such as the words in the Stroop task. This model can account for the results reported, inasmuch as aperiodic noise can be considered novel and is, therefore, more likely to resist filtering and consequently adversely affect performance. The third class of models, the information-processing models, concern a minimum operating level and maximum operating level or channel capacity (Coates, Adkins, & Alluisi, 1975). Information input below or above these levels, respectively, results in degraded performance. However, this model assigns an informational value to noise stimulation based on the number of discriminable changes, e.g., in intensity or frequency, in the stimulus. This model predicts that noise will be processed (and affect task performance) when it is relevant to the task or contains high informational characteristics. The nature of the noise effect will depend on the operating level required by the task and the momentary channel capacity of the subject. This model specifically predicts differential effects due to continuous and high-information timevaried noises. Regardless of the theoretical implications of the present experiment the primary results can be summarized as follows: ( a ) the Stroop-type color-word test does seem to be sensitive to noise effects while many tasks do not, i.e., word reading, in this case, ( b ) some aspect of aperiodic time-varied noise does produce significantly larger decrements in Stroop-type performance than does continuous noise. Further research is, of course, recommended to identify the quality of the color-word test which makes it sensitive to stressors. Some previous suggestions of S-R compatibility effects or perceptual demands seem likely. Further research is also needed to identify the aspects of time-varied noise, e.g., aversiveness, novelty, informational characteristics, etc., which interact with the color-word task to produce decrements, or in other tasks i f these results prove to be of a general nature. REFERENCES BROADBENT. D. E. Effects of noise on behavior. Jn C. W. Harris (Ed.), Handbook o\ noise control. New York: McGraw-Hill, 1957. Pp. 1-33. & ALLUISI, E. A. Human performance and aircraft-type noise interactions. Journal o f Ar~ditoryResearch, 1975, 15. 197-207. FINKLEMAN. J. M., & GLASS,D. C. Reappraisal of the relationship between noise and human performance by means of a subsidiary task measure. Jorrrnal o f Applied Psychology. 1970, 54. 2 1 1-213. HARTLEY, L. R., & ADAMS,R. G. Effects of noise on the Scroop test. Journal o f Experi.menta1 Psychology, 1974. 162, 62-66. HOUSTON, B. K.. & JONES,T. M. Distraction and Stroop color-word performance. Journal o f Experimental Psychology. 1967. 74. 54-56. KIRK,R. E., 8: HECHT.E. Maintenance of vigilance by programmed noise. Perceptrrul and Motor Skills, 1963, 16, 553-560.
COATES, G. D., ADKINS,C. J.,
NOISE EFFECTS O N STROOP TEST
857
O'MALLEY,J. J.. & POPLAWSKY,A. Noise induced arousal and breadth of attention, Perceptual and Motor Skills, 1971, 3 3 , 887-890. TREISMAN,A. M. Strategies and models of selective attention. PsychologicaL Reviezu. 1969, 76, 282-299.
WARNER,H. D., & HEIMSTRA.N. W. Effects of noise intensiry on visual target detection performance. Human Factors, 1972. 14. 181-185. WEINSTEIN,N. D. Effect of noise on intellectual performance. Iournal o f Applied Psychology, 1374, 59. 548-554.
Accepted September 12, 1979.
TIME-VARIED NOISE EFFECTS O N COLOR-WORD TEST PERFORMANCE1 GEORGE D. OGDEN3 A N D ANGELA M. RIECK University of Maryland G L Y N N D. COATES Old Dominion University Summary.-The effects of continuous and time-varied 85 dBA broadband noise o n the performance of a Stroop-type color-word test and a related word. reading task were investigated. 10 subjects served in one of three groups receiving either continuous, periodic, o r aperiodic noise. All subjects performed in both low noise ( 6 5 dBA) and high noise ( 8 5 dBA) conditions on 80 trials of both word reading and color naming. Median reaction times in the word-reading task were unaffected by either noise intensity or the timevaried aspects of the noise. However, median reaction times in the colornaming task were significantly elevated in the 85-dBA noise condition. Also, reaction times in the high aperiodic noise condition were significantly elevated relative to rhe continuous and periodic noise conditions. Results are discussed within the framework of arousal, filter, and information theories.
In 1935 Stroop reported that response times to stimuli, hues written in incongruent color names, were much longer than response times to hue patches. Since that time, the task involving these stimuli, known as the Stroop colorword test, has been reported to be sensitive to various stressors, and this sensitivity has been attributed to the attentional demands of the task. Several investigators have examined the effects of auditory noise on Stroop test performance, but the reported effects of noise have been inconsistent. For example, Hartley and Adams (1974) reported that, althoagh noise had an initial positive effect on Stroop performance, there was a significant detrimental effect on performance during the final 10 min. of a 30-min. session. Other investigators have reported that noise clearly improves performance (O'Malley & Poplawsky, 1971). Houston and Jones (1967) exposed their subjects to 75 dBA of "jibberish" and found that requiring the subjeccs to ignore the noise improved their performance. The conflicting reports of the effects of auditory noise on performance is not, however, restricted to the Scroop task as investigators of the effects of noise on other performances have also reported contradictory results. Noise sometimes improves task performance (Kirk & Hecht, 1963), noise sometimes detrimentally affects performance ( Weinstein, 1974), and quite often, noise 'Supported in part by the National Aeronautics and Space Administration under Research Grant No. NSG-1092, "A Review and Preliminary Evaluation of Methodological Factors in Performance Assessments of Time-varying Aircraft Noise Effects." "eprints may be obtained from George D. Ogden, Department of Psychology, University o f Maryland, College Park, Maryland 20742.
852
G. D. OGDEN. ET AL.
has no effect on performance. Thus, it is noc surprising that noise effects on Stroop performance appear ambiguous, for this accurately reflects the present state of the literature on effects of noise. It should be noted, however, that in the previously described Stroop test experiments, methodological differences, rather than the ambiguous state of noise effects, may account for the divergent results. A wide variety of colorword test forms have been used as well as a wide variety of dependent measures. For example, Hartley and Adams (1974) used a checklist that required subjects to check the correct answer; O'Malley and Poplawsky (1971) and Houston and Jones (1967), on the ocher hand, used verbal responses. Although most of the studies employed total time to completion for all responses as the major dependent variable, Hartley and Adams reported a difference score representing the difference between total time for Stroop color naming and total time for regular color naming. The other source of methodological differences which might account for differences in results concerns the type of noise used. For example, in addition to differences in frequency or intensity of noise, noise can be varied along a temporal dimension. Time-varied noise can be continuous (with little or no variation), periodic (with predictable variations in onset and offset), or aperiodic (with random or unpredictable variations in onset and offset). A number of investigators have manipulated these time-varied aspects. For example, Warner and Heimstra (1972) found that performance on a visual search task improved with the introduction of periodic noise as compared to continuous noise. Finkleman and Glass (1970) found that unpredictable (aperiodic) noise had a detrimental effect on performance when compared to periodic noise in a dual-task performance setting. The purpose of the present st~ldywas to decermine the effects of auditory noise on the performance of a Stroop-type color-word test and a related wordreading task. To assess the effects of the temporal characteristics of the noise as well as the effects of the intensiry level, both aspects of the noise were systematically varied. Further, to maximize the precision of measurement of any possible effects, reaction time to discrete trials was employed as the primary dependent measure.
METHOD The experimental design involved the manipulation of three factors. The first factor was task type, i.e., color naming and word reading; the second faccor was noise level, i.e., low and h ~ g h Subjects performed in all four of these conditions. In the conditions of high noise level, one-third of the subjects were assigned to one of the three subconditions of continuous, periodic, or aperiodic noise. The design was counterbalanced For both order of task and of noise level.
NOISE EFFECTS ON STROOP TEST
853
Subjects were 30 students at Old Dominion University. The sample included 22 females and 8 males; the median age was 21 yr. Subjects were randomly assigned to the temporal subconditions of the high noise level with the stipulation that there would be an approximately equal ratio of males to females in each condition. All subjects had normal hearing and exhibited no color blindness or other visual deficiencies.
Stimuli The stimuli were 80 35-mm slides photographed using Kodachrome-25 film under photolamps (3500' K ) wich a Wratten 80B filter. The stimulus materials were constructed from highly saturated posterboard which provided both lettering and background. The stimuli were constructed wich five hues of letters, i.e., red, blue, green, yellow, and white, that spelled four words, i.e., red, blue, green, and yellow, on Five background colors, i.e., red, blue, green, yellow, and white. The letters, words, and backgrounds were combined factorially, excluding those cases in which the hues of the letters were identical to the hue of the background, to provide the stimulus population. Eqz~ipment The slides were back-projected onto a rear-projection screen and presented at eye level approximately 1 m from the subject. The stimulus presentation duration (750 m m . ) was controlled by a Wollensak shutter (Device 4 H 4 ) . Stimulus presentation activated a Hunter photoelectric cell (Model 31 ) which closed a photoelectric relay (Hunter Model 335s) and started a Hunter digital timer (Model 1521). The timer was stopped by a verbal response into a lnicrophone mounted in front of the subject. A light mounted at the bottom of the rear-projection screen was illuminated briefly approximately 1 sec. prior to stimulus presentation and sewed as a warning signal.
Noise Broadband white noise presented by means of headphones was used for all conditions. The sound pressure level measured at the subject's ear was 65 dBA for the conditions of low noise level. In the condition of high continuous noise, the noise level was set at 85 dBA. Noise in the condition of high periodic noise had an on-off ratio of 50:50 with the "on" intensity at 85 dBA and the "off" intensity at 65 dBA with a complete cycle occurring each second. In the condition with high aperiodic noise, each 1 sec. of noise was selected randomly with equal probabilities from three 1-sec. cycles: ( a ) .25 sec. at 65 dBA and .75 sec. at 85 dBA, ( b ) .5 sec. at 65 dBA and .5 sec. at 85 dBA, and ( c ) .75 sec. at 65 dBA and .25 sec. at 85 dBA. The noise was produced by a white-noise generator (Lahyette Model 1431) and a series of industrial timers and relays were employed to produce
854
G. D. OGDEN, ET AL.
the effects of periodic and aperiodic noise which were recorded on separate reel-to-reel audio tapes. Sound levels were measured at the level of the subject's ear in the headphones, and sound levels were calibrated for each subject in each condition. At the beginning of the experiment, subjeccs were given an audiogram. Normal hearing was defined as having no greater than a 15-dB hearing loss in either ear at any frequency between 500 Hz and 4000 Hz. If the subject demonstrated normal hearing, the experiment proceeded. Each subject participated in two sessions, one session under conditions of Low noise and one session under the High noise condition to which he was assigned; the order in which the subject received the Low and High noise conditions was counterbalanced. Subjects were instrucced as to the nature of their tasks and were given a demonstration of the stimuli and the warning light. In the color-word test, subjects were instructed to respond by giving the color of the letters in the slide. In the word-reading task, subjeccs were instructed co respond by reading the word in the slide. Subjects were instructed to respond as rapidly as possible but not to make any more than two errors in a session. In each session 160 slides were presented, 80 for the word-reading task and 80 for the color-naming task. The order of the tasks was also counterbalanced. There was a 5-min. break between the two sessions, during which the subject was allowed to leave the experimental room. Each session required approximately 30 min. At the completion of the experiment, the subject was tested again for any possible hearing loss that may have occurred from the noise exposure in the experiment; if no threshold shift was evident, the subject was released. The entire experiment lasted approximately 75 min.
RESULTS The primary dependent measure was the median reaction time of the 80 trials of each task. Errors were also recorded, but since the instructions stressed accuracy, very few errors resulted. A total of 56 errors were recorded in the color-naming task (4% of the 12,800 trials), and only 1 error in the wordreading task. Of the 57 errors, 33 occurred under the high-noise conditions and 24 under the low-noise conditions. The efficacy of the experimental counterbalancing of noise order and task order was analyzed. The results of these analyses indicated that neither noise order nor task order had a significant effect on median RT; nor did any of these order effects interact with the experimental factors. The word-reading task and the color-naming task were analyzed separately due to the different task demands and the highly distinctive distributions of
NOlSE EFFECTS ON STROOP TEST
855
RT. The mean of median R T in the word-reading task was 501 msec. (SD = 47.4 msec.) while the mean of the median R T in the color-naming task was 664 msec. (SD = 48.1 msec.).
Word-reading Performances Median R T in the word-reading task were analyzed with a two-factor analysis of variance, with factors of Noise Level (Low and High) and Temporal Condition ( Continuous, Periodic, and Aperiodic). There were no significant main effects due to the level of noise, temporal conditions, nor the interaction of the two factors. Color-naming Performances The analysis of median R T in the color-naming task also employed a twofactor analysis of variance to determine the effects of noise level in each of the three noise conditions. Reliable differences were obtained between the Low Noise and High Noise levels (F1," T 5.27, p < .05). The general effect of the higher noise intensity was to increase RT (or degrade color-naming performance). The mean of median R T in the Low-noise conditions was 655 msec., with a standard deviation of 41.7 msec., and the mean of median R T in the High-noise conditions was 673 msec., with a standard deviation of 53.8 msec. The nature of the noise-level effect was tested for each Temporal condition by means of linear contrasts of the Noise Level X Temporal Condition interaction which was significant (F3,37 = 5.22, p < .01). The average increase in R T between the Low and High noise levels in the continuous and periodic groups was 16 msec. and 25 msec., respectively. These differences were not statistically reliable. However, the increase in R T between the Low and High noise levels in the aperiodic group was 48 msec. This difference was reliable (tls = 2.27, p < .05).
DISCUSSION Theoretical formulations of noise effects on Stroop color-naming are generally of three types. One explanation concerns the arousal theories or the arousal-attention hypothesis, whereby the performance effects due to noise are caused by its activating or arousing properties (cf. Broadbent, 1957). Presumably, arousal narrows attention and, thereby, helps or hinders performance depending on whether the information being filtered is relevant to performance. The present results are consistent with this explanation only to the extent that the level of arousal or activation can be shown to be a function of the timevaried properties of the noise. Selective filter or distraction models (Treisman, 1969) assume that noise affects the perceptual system. The selective filter determines the informational input in the system-which ideally in the Stroop task, would focus on the
856
G. D. OGDEN, ET AL.
color and filter the word. Further, noise that is relevant, intense, or novel may be input into the system causing perceptual inefficiency in filtering "irrelevant" information such as the words in the Stroop task. This model can account for the results reported, inasmuch as aperiodic noise can be considered novel and is, therefore, more likely to resist filtering and consequently adversely affect performance. The third class of models, the information-processing models, concern a minimum operating level and maximum operating level or channel capacity (Coates, Adkins, & Alluisi, 1975). Information input below or above these levels, respectively, results in degraded performance. However, this model assigns an informational value to noise stimulation based on the number of discriminable changes, e.g., in intensity or frequency, in the stimulus. This model predicts that noise will be processed (and affect task performance) when it is relevant to the task or contains high informational characteristics. The nature of the noise effect will depend on the operating level required by the task and the momentary channel capacity of the subject. This model specifically predicts differential effects due to continuous and high-information timevaried noises. Regardless of the theoretical implications of the present experiment the primary results can be summarized as follows: ( a ) the Stroop-type color-word test does seem to be sensitive to noise effects while many tasks do not, i.e., word reading, in this case, ( b ) some aspect of aperiodic time-varied noise does produce significantly larger decrements in Stroop-type performance than does continuous noise. Further research is, of course, recommended to identify the quality of the color-word test which makes it sensitive to stressors. Some previous suggestions of S-R compatibility effects or perceptual demands seem likely. Further research is also needed to identify the aspects of time-varied noise, e.g., aversiveness, novelty, informational characteristics, etc., which interact with the color-word task to produce decrements, or in other tasks i f these results prove to be of a general nature. REFERENCES BROADBENT. D. E. Effects of noise on behavior. Jn C. W. Harris (Ed.), Handbook o\ noise control. New York: McGraw-Hill, 1957. Pp. 1-33. & ALLUISI, E. A. Human performance and aircraft-type noise interactions. Journal o f Ar~ditoryResearch, 1975, 15. 197-207. FINKLEMAN. J. M., & GLASS,D. C. Reappraisal of the relationship between noise and human performance by means of a subsidiary task measure. Jorrrnal o f Applied Psychology. 1970, 54. 2 1 1-213. HARTLEY, L. R., & ADAMS,R. G. Effects of noise on the Scroop test. Journal o f Experi.menta1 Psychology, 1974. 162, 62-66. HOUSTON, B. K.. & JONES,T. M. Distraction and Stroop color-word performance. Journal o f Experimental Psychology. 1967. 74. 54-56. KIRK,R. E., 8: HECHT.E. Maintenance of vigilance by programmed noise. Perceptrrul and Motor Skills, 1963, 16, 553-560.
COATES, G. D., ADKINS,C. J.,
NOISE EFFECTS O N STROOP TEST
857
O'MALLEY,J. J.. & POPLAWSKY,A. Noise induced arousal and breadth of attention, Perceptual and Motor Skills, 1971, 3 3 , 887-890. TREISMAN,A. M. Strategies and models of selective attention. PsychologicaL Reviezu. 1969, 76, 282-299.
WARNER,H. D., & HEIMSTRA.N. W. Effects of noise intensiry on visual target detection performance. Human Factors, 1972. 14. 181-185. WEINSTEIN,N. D. Effect of noise on intellectual performance. Iournal o f Applied Psychology, 1374, 59. 548-554.
Accepted September 12, 1979.
