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|Year : 2003
: 6 | Issue : 21 | Page
|Noise and mental performance : Personality attributes and noise sensitivity
G Belojevic, B Jakovljevic, V Slepcevic
University of Belgrade, Faculty of Medicine, Institute of Hygiene and Medical Ecology, Serbia,
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The contradictory and confusing results in noise research on humans may partly be due to individual differences between the subjects participating in different studies. This review is based on a twelve year research on the role of neuroticism, extroversion and subjective noise sensitivity during mental work in noisy environment. Neurotic persons might show enhanced "arousability" i.e. their arousal level increases more in stress. Additional unfavorable factors for neurotics are worrying and anxiety, which might prevent them coping successfully with noise, or some other stressors during mental performance. In numerous experiments introverts have showed higher sensitivity to noise during mental performance compared to extroverts, while extroverts often cope with a boring task even by requesting short periods of noise during performance. Correlation analyses have regularly revealed a highly significant negative relation between extroversion and noise annoyance during mental processing. Numerous studies have shown that people with high noise sensitivity may be prevented from achieving the same work results as other people in noisy environment, thus leading to psychosomatic, neurotic or other difficulties. Positive relation between noise annoyance and subjective noise sensitivity might be very strong. Our results have shown, after matching with the results of other relevant studies, that more stable personality, with extroversive tendencies and with a relatively lower subjective noise sensitivity measured with standard questionnaires, may be expected to better adapt to noise during mental performance, compared to people with opposite personality traits.
Keywords: Noise, performance, personality, sensitivity, humans
|How to cite this article:|
Belojevic G, Jakovljevic B, Slepcevic V. Noise and mental performance : Personality attributes and noise sensitivity. Noise Health 2003;6:77-89
| Introduction|| |
According to William James (1890) "the mind, in short, works on the data it receives, very much as a sculptor works on his block of stone. In a sense the statue stood there from eternity. But there are a thousand different ones beside it, and the sculptor alone is to thank for having extricated this one from the rest… Other sculptors, other statues from the same stone! Other minds, other worlds from the same monotonous and inexpressive chaos!"
With the kind of anatomical, physiological and neurological systems Man as a species possesses, he can adapt himself to almost any environment, solve almost any problem. In contrast, man as an individual is limited. This is not necessarily because he lacks any of the potentialities we attribute to the human species, but because he lacks time (Murphy, 1958).
Each individual begins with one particular fraction of the human gene pool, facilitating development in some directions, retarding it in others. Broad social policies, differing from one period to another, help to determine which human potentialities individuals will be encouraged and stimulated to develop. We are witnessing in our time one of these major policy changes. Due to automation and information "boom" in all parts of society, fewer and fewer personalities with superior physical strength and manual skills are needed, but more and more people with superior ability to manipulate symbols i.e. to think.
By the term - "mental performance", various forms of reaction may be considered (e.g. control activity, rapidity of reaction, learning, memorizing or intelligence). While perceptual or motor performance involves primarily muscular activity or sensorial responses, mental or cognitive performance is primarily based on mental activity.
In mental performance there are several stages: 1) sensory processes, 2) perceptual and attentional, 3) short term memory, 4) long term memory, 5) central and specific processors. Out of the huge amount of information detected by sense organs during a cognitive task, some parts are identified, selected and organized through perceptual and attentional processes. In further processing, relevant data may be "filed" and compared with those already kept in long term memory. In tasks with the highest mental load, thinking i. e. central processing of these data, is required in order to select and execute the appropriate response. In all stages there are individually determined capacity limitations which may lead to disturbance by some intrusive factors on processing (Gamberale et al. 1990).
In its nonverbal and verbal forms, the auditory environment is vital for human functioning at both cognitive and emotional levels. In nonverbal noise physical components dominate, while in verbal noise semantic components dominate. On the other hand, auditory stimulation can become a highly destructive source of negative experiences. Auditory stimulation may include physical and semantic components that cause frustrating, irritation and inefficiency. They may become a serious threat to our wellbeing and health. Due to intensive industrialization and urbanization followed by traffic "boom", noise or "unwanted sound" (Burns 1973) has become a ubiquitous stressful factor, both in living and in occupational environments. The public sees this trend as a serious threat to human well being, so that in opinion polls noise has regularly been ranked among the most annoying single environmental problems.
In the occupational environment, noise is a major noxious factor. In highly industrialized countries like Sweden about 40% of the total work force consider themselves to be exposed to noise. For males it is 68%, and even for white collar workers it is about 25%. However, physical noise measures are usually found to explain only 14%-25% of the variance in workers annoyance (Kjellberg et al 1988, Kjellberg 1990).
Due to noise abatement policies, the number of workplaces with high noise levels is expected to decrease in most countries. Noise levels at 90 dB and above are of limited practical interest in performance studies, as these levels should be avoided in working milieu for reasons of hearing protection.
However, at many previously quiet workplaces the new sources of moderately loud noise have been introduced, namely various automates, instruments, computers, printers, ventilation systems etc. For instance, in a modern operating theatre, which is generally regarded as quiet (Leq about 50 dBA), Hodge and Thompson (1990) have found 27 sources of sound, with peak levels ranging from 52 to 108 dB. This revolution in automation has given priority to manipulating symbols instead of tools i.e. to mental over physical work. This is why it may be assumed that mental performance in moderately loud noise might be more and more frequent problem in occupational hygiene. Although Broadbent (1957) concluded that no detrimental effect of noise on performance should be expected at levels lower than 90 dB, contemporary research tends to doubt this claim. Depending on the complexity and nature of a task, the experimental setting and the choice of subjects, noise levels sufficient for performance intrusion could be lowered to 51 dB(A) (Kjellberg and Wide, 1988).
Noise is a highly relative construct. There is a common denominator, however: unwanted sound. Noise induced stress means that the organism is unable to ignore, block out or otherwise cope with the unwanted sound, or that it is able to do so only at a cost. There are two major, relatively independent target areas for noise research:
Noise affects the person who is "doing nothing" by annoying him.
Noise affects the person who works by impairing his performance or making it more costly in terms of increased effort.
Against this background, studies on the importance of noise for work performance have a high priority in occupational medicine. The aspects of main interest in the studies of the effects of the work environment on performance may be: productivity effects, safety risks or mental and neurological functioning. The objects of main interest may be identification of sensitive individuals or identification of environments that lower productivity or have high accident risk or are hazardous to health and well being. Practical individual problems have provided the impetus for such studies and their principal aim has been to improve productivity and the quality of job performance, by providing a suitable physical work environment. Performance measurement may also be used for predicting accident risk or as an indicator of the state of various CNS functions. When safety risks are to be assessed, it is necessary to observe performance in the real work task or a simulation of that task. If on the other hand, the aim is to assess mental or neurological functioning, the realism of the task is of little consequence (Gamberale et al 1990).
| Studies of Mental Performance|| |
The contradictory and confusing results in noise research may partly be due to individual differences between the subjects participating in different studies. It is a well-known everyday experience that people react to noise in different ways. Some are seriously disturbed, others are not affected at all and still others might even improve their performance. Such opposing trends for subgroups mask each other and perhaps lead to the incorrect conclusion that noise does not affect performance (Auble and Britton 1958).
With respect to general intelligence, it is assumed that less able subjects would be more susceptible to harmful effects of noise, because they probably are more dependent on task relevant information than the more able subjects. Furthermore, when doing mental work in noise, they probably have less resources to call upon, while the more able subjects can exploit their resources if the need arises.
Studies on people living in areas with a high level of aircraft-noise showed that their everyday errors (failures of attention, memory and action) appear more frequently, compared to people living in low-noise areas (Smith and Stansfeld 1986). Children in noise-impacted areas have been shown to display impaired mental performance, including incidental learning and visual search (Heft 1979), reading achievement (Green et al. 1982), and puzzle solving (Cohen and Weinstein 1981). Self-reports of everyday errors (failures of attention, memory and action), given by people in an area with high aircraft noise and those of a similar group who lived in an area with a low level of noise, the high noise group reported a greater frequency of everyday errors (Smith and Stansfeld, 1986). An interview cross-sectional study carried out on 413 residents in the centre of Belgrade showed the significant behavioral effects of road traffic noise (Leq>65 dB (A)) in terms of more frequent intention to change the place of living, shortening the daily period of open windows and worse interpersonal relationship between dwellers (Belojevic et al. 1997).
In the occupational environment, noise impairs tasks involving a high mental load and high control precision, has no effect on manual dexterity and even facilitates tasks involving physical strength (Levy-Leboyer and Moser, 1988).
One of the earliest field studies on effects of noise on performance showed that, over the course of one year, weavers (10) with normal hearing, who wore earplugs in 96 dBA industrial noise, had better loom output (quantity and quality of the cloth) than those who had no hearing protection (Weston and Adams 1935). It has been reported that workers in textile mill departments with high noise levels (above 90 dBA) showed slightly lower productivity (1.24%, p<0.01) than those in departments with lower noise exposure (below 90dBA) (Noweir 1984). In an earlier study in a film production plant, noise reduction at workplace led to a significant drop in the frequency of workers' errors. Noise does produce human errors, even in those who are used to it (Broadbent and Little 1960). A field experiment in the room used for postal letter sorters showed a significant positive correlation between the level of noise emitted via loudspeakers and the number of sorting errors (Kovrigin and Mikheyev 1965). There is a questionnable effect of noise on mental performance that does not require audition, because there is no masking effect. Broadbent showed that noise had to reach a level of about 90 dB before it could affect nonauditory work performance. High frequency sounds, above 2000 Hz, had larger effect on people than sound frequencies below 2000 Hz (Broadbent 1961).
As numerous environmental and other factors besides noise might influence performance in field studies, laboratory experiments with strictly controlled conditions must initially be used for the evaluation of possible causal connection of noise and performance. Even if experimental conditions have thus been better controlled, numerous discrepancies and controversies can be recognized in laboratory studies (Loeb 1981, Eysenck 1982, Dornic 1990, Kjellberg 1990b). Thus, noise levels ranging from 50 to 110 dB have been reported to deteriorate (Baker et al. 1984, Sandover and Champion 1984), not to affect (Kryter and Poza 1980, Gawron 1984) or even to improve (Hockey 1970, O'Malley and Poplawsky 1971) speed or accuracy of mental performance in laboratory settings. It has been more often an exception than a rule to replicate the findings in these studies, thus limiting the possibility of drawing general conclusions and making exact predictions.
A mental task may require comparing of physical characteristics of stimuli which is referred to as shallow, superficial or physical processing. Another type of mental task involves the comparing meanings of stimuli (e.g. do they belong to the same semantic category), and this is referred to as deep or semantic processing. Findings have been reported that noise may deteriorate semantic processing while not affecting, or even facilitating physical processing (Dornic 1975). This is what is to be expected , since deep processing requires more time than superficial processing. Thus, by definition, deep processing is more difficult and as such should be more affected by any stress, including loud noise. Still, some experiments have failed to confirm this finding (Daee & Wilding 1977, Smith & Broadbent 1981, 1982). It has been widely accepted that changeable noise is more detrimental to performance, compared to a steady noise of a same level (Kirk and Hecht 1963).
| Personality Attributes and Tolerance to Noise|| |
One of the fundamental assumptions of modern psychology is that the same situation affects different persons in different ways (Tyler 1965). Area in which individual differences are striking is information processing. High information load, or task stress enhances these differences. If information stress is combined with other stresses, e.g. noise, further increase in individual differences can be expected. Some individuals will be little affected, some may even improve their performance. The efficiency of most people will be decreased, either in terms of performance, or in terms of effort expenditure. What do these striking differences in stress tolerance depend on?
Basic personality traits are at least moderately consistent through lifetime. A large amount of evidence about the stability of all kinds of psychological traits has been assembled and organized by Bloom (1964). In spite of numerous controversial data reported over the years, this approach appears to pervade a highly useable framework for the study of individual differences in stress tolerance. A major assumption is that extroversion is intimately related to chronic level of cortical activity, while neuroticism (often thought as a synonym of anxiety) is linked to "arousability", i.e. to an increase in arousal level when stress is applied. In the studies on individual differences in stress tolerance, researchers have frequently used stable (non-neurotic) extroverts and neurotic introverts, respectively, as personality types representing opposite extremes on a general arousal continuum: the former are assumed to have low chronic cortical arousal and low situational arousability, while the opposite applies to the latter. The logic of the theory requires that low-arousal individuals tend to seek external stimulation ("arousal seeking behavior", or "stimulus hunger"), and therefore are able to tolerate more stress than high-arousal individuals, who typically avoid intense and/or frequent external stimulation.
| Neuroticism|| |
The first and broadest of the personality variables to be measured in many ways is general neuroticism or emotional instability. This trait has been thoroughly defined and described by factor analytic method (Eysenck 1947). One of the most valuable contributions made by Eysenck's work of delimiting and defining this variable has been the clear separation of the tendency toward neurosis from the tendency toward psychosis or complete mental breakdown. Eysenck has clearly showed that neurotic and psychotic tendencies are two completely different dimensions of personality, though both are conditions with traits existing in normal people. Tests defining the neuroticism factor in normal individuals differentiate clearly between diagnosed neurotics and normals, but they do not differentiate at all between diagnosed psychotics and normals. All of us probably have a certain amount of both traits as a part of one basic human nature. Because the two tendencies are independent, we must not use the one as an indicator of the other. Neuroticism, a personality attribute that is fairly consistent through lifetime (Bloom 1964), has been related to tolerance to noise. Mandler and Savason (1952) showed that when more complex material was being learned, the main personality variable of importance appeared to be neuroticism rather than extroversion. Cohen et al. (1966) pointed out that subjects who were found on personality tests to be anxious, introverted and somatic responsive, were more adversely affected by noise in the vigilance tasks than were the better adjusted subjects.
Neuroticism is often thought to be reflected in self-oriented thoughts, worry and anxiety, each of which act as a distracter from learning and recall. The personality variable of neuroticism, measured with the EPI scale, was found to be positively correlated with subjective noise sensitivity and annoyance during noise exposure (Ohrstom et al. 1988). In more complex mental tasks such as retrieval from semantic memory (von Wright and Vauras 1980), or learning of a passage of prose (Nurmi and von Wright 1983), neurotics have displayed worse performance in noise compared to stable individuals. It is not possible to explain this result in a simple way. Neurotic persons' CNS might normally be under a bigger extent of arousal, so the crucial level of arousal could be more easily reached by noise than in normals.
Neurotic persons might show enhanced "arousability" i.e. their arousal level increases more in stress (Eysenck 1967, 1977, 1982). Additional unfavourable factor for neurotics are worrying and anxiety, which might prevent them coping successfully with noise, or some other stressors during mental performance.
| Extroversion|| |
Jung first used the terms extroversion and introversion in his exposition of psychological types. Extroversion refers to the kind of outward orientation that makes a person highly aware of what is going on around him and causes him to direct his energy toward objects and people outside himself. Introversion is an inward turning tendency that makes a person sensitive to his own feelings and experiences and causes him to direct his efforts toward understanding them. According to Jung's reasoning, extroversion and introversion are not mutually exclusive categories. Both trends are a part of everyone's psychological make-up, and if one of them is not in evidence in behavior, he looks for signs of its unconscious operation. Furthermore, Jung did not equate extroversion with sociability, as many psychologists have done. For Jung, the introvert was not necessarily shy, seclusive or socially maladjusted. When social behavior is used as the touchstone, introversion becomes confused with the neuroticism. Eysenck (1947) came out with much more solid evidence that introversionextroversion is a meaningful basic dimension of personality continuum, using objective personality tests and factor analysis method.
Eysenck (1970) suggested that tolerance and preference noise levels differ in introverts and extroverts. Those who are classified as introverts have been shown to have a lower optimum arousal threshold and therefore do not need much stimulation before passing their optimum functioning level. Those who are extroverts have higher optimum arousal thresholds and therefore tend to seek arousal or stimulating situations. Stelmach (1981) reviewed the extensive psychophysiology evidence that supports the hypothesis. Gray (1964) linked these categories with the Russian ideas of strong (extrovert) and weak (introvert) nervous systems. In fact, Gray's (1981) theory suggests the anxiety (neuroticism) may act as a mediating factor between extroversion and task performance. VermonlayevaTomina (1964) found that those with a strong nervous system tended to learn more in distracting situations than those with a weak nervous system. Geen (1984) showed by using a technique that allowed subjects to adjust the level of noise to an optimum, that extroverts selected higher intensities. In another study it has been demonstrated that when studying in library, introverts were significantly more likely to choose a place to work away from the bustle of certain areas, while the extroverts were more attracted to the latter as a work place (Campbell and Hawley, 1982). This provides further evidence of the regulation of arousal differences between introverts and extroverts. Introverts are more aroused normally and are affected in performance only if noise exceeds its optimum, for extroverts it is the case if noise diverges from noise in both directives.
Introverted persons were shown to have more sensitive auditory thresholds (Smith 1968), while extrovert adults (Hockey 1972) prefer higher level of noise input. In numerous experiments introverts have showed higher sensitivity to noise during mental performance compared to extroverts (Shanmugan and Santhanam 1964), while extroverts often cope with a boring task even by requesting short periods of noise during performance (Davies et al. 1969). Morgenstern, Hodgson and Law (1974) found that extroverts actually performed better in the presence of distractions than they did in silence, while introverts showed a deficit in performance. Their participants were asked to attend to, and remember, a number of words out of a long list that was read to them, whilst they were being read a passage by the same voice. They were given a means of controlling the balance of sound between the word list and the passage, but the greater this difference the more the words to be remembered were distorted. This finding was consistent with Eysenck's theory that the introvert's nervous system is over-damped.
More recently, Furnham, Gunter and Peterson (1994) conducted a study into the effects of the presence of an operating television on introverts and extroverts, while they completed reading comprehension tasks. They found, as predicted, a significant interaction, F (1,39)=7.41, p<0.01, between the personality dimension and the treatment effect. In other words, the introverts and extroverts performed equally well with the television off, but the extroverts performed better then the introverts when the television was on.
In an early experiment in this area, Daoussis and McKelvie (1986) found that, although extravert subjects reported working with music twice as much as introverts (50% versus 25% of the time), both groups reported playing background music very softly. Both groups were given a reading recall test in which they were instructed to spend 10 minutes reading a paired associate learning task in noise. It was shown that introverts were likely to be affected in performance only if noise exceeded its optimum. In a mental arithmetic task applied on 123 medical students under quiet (42 dB(A) Leq) and noisy laboratory conditions (recorded traffic noise, 88 dB (A) Leq), extroverted subjects performed significantly faster in noise. In introverted subjects, concentration problems and fatigue were more pronounced in noise. Correlation analysis revealed a highly significant negative relation of extroversion and noise annoyance during mental processing (Belojevic et al 2001). Geen (1984) has reported that individuals scoring high on extroversion chose or preferred higher levels of sound or noise than those scoring low. In these experiments extroverts were usually affected if noise diverged from optimum in both directions.
Weinstein (1978) has questioned whether "the link between introversion and noise sensitivity is due to direct arousing effect of noise on the central nervous system, or to the fact that noise frequently has interpersonal significance and is seen as an intrusion by those who are ill at ease in social settings and prize privacy (psychosocial effect)". This point is particularly pertinent in the light of psychological research showing that personality factors such as introversion-extroversion are important mediators of individual cognitive performance in the process of distraction (Morgenstern et al., 1974).
| Subjective Noise Sensitivity|| |
It is commonly believed that, in a long-term perspective, people will adapt to noise in the sense that they become less annoyed by it. In fact, most evidence speaks against such an effect, at least after the first few weeks in a new environment (Weinstein, 1982).
Noise sensitivity - what is it? The existence of individual differences in sensitivity to noise appears to be a commonplace confirmed both by abundant anecdotal evidence and by psychological research (e.g. Levy-Lebover, Verdrene & Veyssiere, 1976; Goldstein & Dejoy, 1980). Beyond this simple statement, however, the question of individual differences in noise sensitivity turns out to be a complex one.
To begin with, it is important to ask: what are our conclusions about these individual differences based on? The most obvious and straightforward basis for such conclusions in real-life settings is people's complaints. While tendency to complain may be related to the intensity of the annoyance the person is complaining about (e.g.Weinstein, 1978), complaints about noise need not necessarily reflect genuine noise sensitivity. People tend clearly to differ in "critical tendencies" (Weinstein, 1982) which are related to other individual characteristics (e.g. LevyLeboyer et al, 1976). In any case, it is important to distinguish between complaint behavior and annoyance (Cohen and Weinstein, 1981).
Anderson (1971) defined sensitivity to noise as a factor underlying attitudes toward noise in general. The terms "subjective noise sensitivity" (McKennel and Hunt 1966) and "noise annoyance susceptibility" (Moreira and Bryan 1972) have been defined either by direct questioning or using standardized questionnaires. In measuring noise sensitivity, it has been shown that longer questionnaires, such as Anderson's Personal Sensitivity Section of the General Noise Questionnaire (1971), Bregman and Pearson's Noise Annoyance Sensitivity Scale (1972) and Weinstein's Noise Sensitivity Scale (1978) have better predictability of annoyance reactions under noise than short questionnaires (Griffiths and Delauzun 1977). Psychometric properties (reliability, internal consistency, factor structure and construct validity) of the Swedish version of the Weinstein's Noise Sensitivity Scale were satisfactory. Sample comprised 236 students (77% women) of the University of Stockholm. Total scale mean was 57.5±12.6, range 25 -90. Normal distribution was obtained. The reliability estimates were of the same magnitude as those reported by Weinstein (1978). The interim correlation was mainly positive, with an average correlation coefficient of 0.21. The item - total correlation was positive and high - 0.11-0.73. The nature of the scale was confirmed to be unidimensional. External validity (generalizability) of the Weinstein (1978) findings is supported (Ekehammar and Dornic, 1990).
However, the complex and multidimensional nature of noise sensitivity as a personality attribute creates difficulties to measure it in unambiguous terms. In a specific situational context, subjective noise sensitivity might be influenced by meaning of noise, mood, motivation and other variables (Levy-Leboyer et al. 1976, Cohen and Weinstein 1981). Nevertheless, a relative consistency and stability in a general level of noise sensitivity seems to exist. In favour of this assumption is the reported high correlation (men=0.63, women=0.74) of test-re-test scores on Noise Sensitivity Scale, among the residents of London, after a threeyear period (Stansfeld 1988). The investigation among residents along a highway prior and 4-16 months after its opening showed no evidence of adaptation of self-reported noise effects, annoyance or tendency to focus attention on the noise (Weinstein 1982). This could mean that a part of population tends to remain poorly adaptive to noise for longer periods of time.
Measuring performance on a laboratory task in the presence and absence of noise is an indirect way of assessing sensitivity to noise. If a person's performance deteriorates under noise the conclusion can be drawn that he/she is more sensitive to noise than another person, whose performance does not impair under noise. However, this assumption can hardly be generalized beyond the particular situation. Besides, there may be contamination by a number of extraneous variables such as motivation, momentary mood, attitudes, and so on. And there is intraindividual variability associated with time of day and gender (Baker, Holding and Loeb, 1984; Davies and Davies, 1975) and other situational factors (c.f., LevyLeboyer et al, 1976). In an interview cross sectional study on a sample of 413 inhabitants of Belgrade, ten-graded annoyance scale, Weinstein's Noise Sensitivity Scale and the Eysenck Personality Questionnaire were applied. Distribution of noise sensitivity scores was normal and independent of noise exposure. No significant differences in average noise sensitivity scores were observed concerning gender and exposure to low (Leq<55 dB (A), and high level of traffic noise (Leq>65 dB (A). Multiple regression analysis revealed that neuroticism was the best individual predictor of subjective noise sensitivity, for both sexes in the noisy area and for women only, in the quiet area. Age, education level and introversion were not significantly related to noise sensitivity. Positive relation between reported noise annoyance and noise sensitivity was highly significant (Belojevic and Jakovljevic 2001).
Various criteria have been used to explain individual differences in noise sensitivity. One of them is the auditory acuity, but it seems that there is no significant relation between auditory thresholds as measured by audiometer and subjective noise sensitivity, although necessarily severe hearing impairment will reduce annoyance reactions to noise (Stansfeld et al. 1985). This favors the assumption that subjective noise sensitivity is a function of cognitive process rather then merely a function of a peripheral auditory acuity.
Subjective noise sensitivity and noise annoyance were shown to be related to complaint behavior (Weinstein 1978), but the criticism toward the environmental factors, including noise might be influenced by other subjective variables besides noise sensitivity (Levy-Leboyer et al. 1976). Therefore, complaint behavior and subjective noise sensitivity are not directly related (Cohen and Weinstein 1981). Noise sensitivity, as a subjective variable, is likely to be randomly distributed with respect to age, sex, social class, education and job responsibility (Moreira and Bryan 1972, Taylor 1984). It also seems that differences in sensitivity to noise are not confined to noise nuisance only, but could be extrapolated to other environmental nuisances (Langdon 1976), as noise sensitive persons tend to express higher criticism toward their environment in general (Weinstein 1982). The correlation between noise-sensitivity scale and the personality tests revealed that sensitivity to noise clearly has much in common with a desire for privacy and that the tendency to be bothered by noise is related to a tendency to express annoyance about a wide variety of nuisances. Noise sensitive subjects were shown to be generally lower in dominance, capacity for status, sociability and social presence. In investigating the personal attributes of highly noise sensitive persons it was shown that they have significantly less intellectual ability, fewer social skills, and a stronger desire for privacy than those who are not sensitive. Noise sensitive individuals are more likely to be critical of their surroundings and to express annoyance about situations generally recognized as being irritating (Weinstein 1978). It is questioned whether the modest link between introversion and noise sensitivity is due to direct arousing effects of noise on the central nervous system, or to the fact that noise frequently has interpersonal significance and is seen as an intrusion by those who are ill at ease in social settings and prize privacy (psychosocial effect). Weinstein's Noise sensitivity Scale was applied in 215 Swedish students (77% female). Mean NSS score was 57,54 ± 12.61 (0-5). All 21 items were in negative correlation to extroversion and 17 statistically significant (p<0.10). The relation between total NSS score and extroversion was highly significant (p<0.001). There was a marginally significant positive correlation between noise sensitivity and neuroticism, but it disappeared when controlling for extroversion. (Dornic and Ekehammar, 1990).
An important question is whether there may be a relationship between noise sensitivity and other traits or personality characteristics that would make it possible to predict the individual's responses to noise in as many situations as possible. On the whole, research into this problem has brought about few unambiguous results. Most of the data reported up to now are inconclusive and often conflicting. The number of studies in which a clear relationship between noise sensitivity and some other relevant variable has been found is small. For instance, Weinstein (1978) found self-reported noise sensitivity to be associated with intelligence, self-confidence in social interactions and need for privacy. Noise annoyance scales have been used as a measure of neuroticism, but Broadbent's selective review (1971) points out inconclusive and controversial nature of such a relationship.
Iwata (1984) reported that individuals whose level of noise sensitivity (as measured by a scale) was high, tended to be less healthy than those displaying low level of noise sensitivity. Iwata also found that noise-sensitive people were those who could be identified as maladjusted personalities. On the other hand, no simple or obvious relationship was found between sensitivity to noise (in terms of annoyance) on the one hand, and age, sex, education, income and job responsibility, on the other. This is true both of community noise surveys (Weinstein, 1978), and of a laboratory study (Moreira & Bryan, 1972). In the latter study, the above listed variables did not appear to be related to personality traits as determined by the EPI and the MMPI, but were related to some personality measures derived from the Rorschach test More Details.
Jelinkova et al (1988) showed that noise sensitive people had a reduced work ability and attention when exposed to recorded traffic noise at a level of 75 dB (A) Leq, compared to persons tolerant to noise. In another field study, in which noise sensitivity was linked to complaints about chronic exposure to environmental noise, complainers were shown to perform worse on a vigilance task than non-complainers (Poenary et al. 1987). Although Dornic et al. (1989) failed to confirm that subjective noise sensitivity correlated with performance on vigilance, information processing, reasoning and incidental learning tasks, they found that irritation by noise and general annoyance during performance were significantly higher in noise-sensitive persons. This relation between noise annoyance and subjective noise sensitivity has been shown to be very strong (Ohrstrom et al. 1988), presenting a possible clue in the explanations of the individual differences in performance in noise. An experimental study on students performing four cognitive tasks under recorded traffic noise (Leq = 55 dB (A) and 75 dB (A)) showed that subjective noise sensitivity was the primary factor responsible for significant differences in mental performance in a short-term memory and a mental arithmetic task (Belojevic et al 1992). Although annoyance has generally been regarded as a dependent variable in noise studies, it might act as an intermediate factor as well (Gulian 1973), as annoyance is likely to have a feedback on the psycho-physiological state and thus on performance, just as performance level has a certain influence on annoyance level and arousal.
Noise annoyance as a negative attitude towards a specific noise or noisy environments, is a feeling of displeasure associated with actual noise, which may have a general additive effect, enhancing arousal, distraction and masking during mental performance. Furthermore, it might force the performer to work faster even at the cost of less accuracy, in order to get rid of the unpleasant situation as soon as possible. Annoyance may as well absorb a part of processing capacity that will then not be available for the task, or for coping with intrusion by noise (Dornic 1977, Eysenck 1982). When considered at all, annoyance has typically been dealt with as a dependent variable parallel to performance, rather than a possible mechanism underlying or mediating the effect of noise on information processing (i.e. intermediate variable). Noise-induced annoyance is likely to affect processing efficiency in several ways. It may further increase arousal triggered by noise and enhance the effects of distraction and masking. Apart from these general, additive effects, annoyance is likely to have an effect of its own. For instance, it may absorb a part of processing capacity that will then not be available for the task (Dornic 1977, Eysenck 1982). Second, annoyance may prompt the performer to work faster, even at the cost of adapting a more risky decision criterion, in order to get rid of the aversive situation as soon as possible.
In summary, noise may prevent people with high noise sensitivity from achieving the same work results as other people, thus leading to psychosomatic, neurotic or other difficulties. In that case, long-term noise abatement policies should be aimed to adapt work places to more sensitive workers. Noise sensitivity appears to be a complex, multidimensional personal characteristic, possibly stable, but subject to situationally determined (and therefore considerably variable) cognitive and affective factors involving meaning, attitudes, motivation and so on. It is also clear that different criteria, such as annoyance and performance, need not necessarily yield an identical picture of an individual's noise tolerance.
| Conclusion|| |
Mental performance in noise is influenced by a network of interrelated factors classified in three major groups: characteristics of a task, environment and personality. In a twelve year research period we have concentrated on individual differences in adaptation to noise during mental work, namely on the role of neuroticism, extroversion and subjective noise sensitivity. Our results have shown, after matching with the results of other relevant studies, that more stable personality, with extroversive tendencies and with a relatively lower subjective noise sensitivity measured with standard questionnaires, may be expected to better adapt to noise during mental performance, compared to people with opposite personality traits.
| Acknowledgments|| |
This review is a result of the the following three consecutive projects:
Effects of noise on work performance with regard to subjective noise sensitivity, 1990-1991, Department of Environmetal Medicine, University of Gothenburg (financially supported by the Swedish Work Environment Fund). The effects of road traffic noise on mental health of an urban population, 1993-1996, Institute or Hygiene and Medical Ecology, Faculty of Medicine, University of Belgrade (Ministry of Science and Technology, Republic of Serbia). Psyhophysiological effects of noise, 1996-2000, Institute or Hygiene and Medical Ecology, Faculty of Medicine, University of Belgrade, (Ministry of Science and Technology, Republic of Serbia).
Goran Belojevic was the Lead Investigator in these projects.
The authors are thankful to Swedish colleagues from the Department of Environmental Medicine, University of Gothenburg:
Prof Evy Ohrstrom for substantial role in designing and performing the experiments as well as in writing investigation report and a scientific paper,
Prof Ragnar Rylander for support, supervision and advices during the investigation,
Mr. Martin Bjorkman, PhD, Civil Engineer, for technical support in designing and performing human experiments and Ms. Ann Brit Skanberg, for assisting in research data input.
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Institute of Hygiene and Medical Ecology School of Medicine, University of Belgrade Dr Subotica 8, 11000 Belgrade, Serbia
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