Crowding And Other Environmental Stressors Research Paper

The construct of psychological stress has proven useful for understanding how the physical environment can affect human well-being. Psycho-logical stress refers to behavioral and physiological reactions to environmental demands that exceed or tax the adaptive capacities of the organism. These demands are termed stressors. Adaptive capacities of the organism encompass genetic predispositions, cognitive and behavioral coping strategies, and social characteristics (e.g., social support) that can alter the balance between environmental demands and individual capacity.

1. Psychological Consequences Of Crowding, Noise, And Air Pollution

The primary index of crowding is residential density (people room). Other measures of crowding, particularly those at a larger scale, such as people per acre, have proven inconsequential for health and behavioral outcomes. This is one reason why demographic and epidemiological approaches to crowding and health have largely proven futile—for example, density statistics based upon census tract data are typically uncorrelated with a host of health outcomes, including disease, mental illness, and crime (Evans in press). Use of aggregate level density indices also leads to misleading cross-national comparisons of crowding and pathology. As an illustration, comparisons of crime rates across countries reveal lower crime rates in Hong Kong in comparison to the USA even though the number of people per acre in the USA is markedly lower than people per acre in Hong Kong. On the other hand, people per acre in Manhattan is not lower. Most likely it is the immediate experience of unwanted or uncontrollable social interaction that lies at the root of the crowding experience. This can be illustrated by the following dilemma: Would you rather share a very large room with one other person or have a small, even cramped room for yourself? Exposure to traffic congestion may be a related form of crowding stress largely caused by interference with progress towards one’s destination. In this case exposure to peak traffic levels rather than average levels of congestion is decisive.

Noise, which is defined as unwanted sound, is usually measured in terms of sound intensity metrics such as decibels (dBA). Both average levels of sound intensity (Leq or Ldn) as well as peak levels of sound intensity exposure appear to be consequential. Leq is an arithmetic average, and Ldn is a weighted average incorporating a night time noise exposure penalty. Ldn is the most typical index of noise exposure used around airports in the USA. It is important to note that decibels is a logarithmic scale. An increase of 10 dBA is perceived as approximately twice as loud. In terms of hearing loss, the duration of exposure is as important if not more so than the actual level of sound intensity, unless extreme. Unfortunately, the implications of exposure duration for stress effects of noise have received insufficient attention.

Air pollution exposure is measured by atmospheric concentrations of known pollutants (e.g., sulfur di-oxide) or toxins that are a major constituent of pollution (e.g., ozone as a component of photo-chemical smog). Both average levels of exposure as well as peak exposure levels are of importance for human well-being.

Precise estimation of individual exposure to environmental stressors like crowding, noise, and air pollution has proven difficult because of spatial and temporal mobility of human samples. Ambient air pollution illustrates well the challenge of accurate exposure estimation. Not only do people move around during the day, they spend time commuting as well as transferring back and forth between interior and outdoor settings. Each of these factors alters personal exposure to ambient pollutants.

For all three environmental stressors, human psychological functioning has been assessed across a range of experimental studies in the laboratory, cross-sectional field studies and, in a few instances, longitudinal studies with assessments of changes in exposure associated with outcomes of interest. Therefore caution is warranted in interpreting the conclusions described here since many of them are based primarily on acute, short term laboratory studies, or on cross-sectional field comparisons. On the other hand, convergence between laboratory and field studies is generally high (Evans 2001).

1.1 Psychophysiological Stress

Both laboratory and field research indicate that high density elevates blood pressure and neuroendocrine indices (e.g., epinephrine) of stress. Trends suggest that these effects are heightened for males and can occur in children as young as six years of age (Baum and Paulus 1987, Evans 2001). Parallel psycho-physiological data have been found in field studies of traffic congestion.

Acute noise elevates cardiovascular and neuroendocrine parameters, but these effects rapidly habituate unless experimental participants are placed under moderately intense physical or cognitive demands. There is also some evidence that noise-sensitive individuals do not readily habituate to acute noise exposure. Cardiovascular data from occupational noise exposure are inconsistent and lie on a foundation of poorly designed studies rendering definitive conclusions impossible. Better designed com-munity studies show modest elevations in blood pressure associated with airport noise exposure. Interestingly, these psychophysiological effects do not habituate with longer exposure duration. Most of the community noise studies have examined children attending elementary schools in airport noise-impact zones. Few community studies have examined adults or neuroendocrine parameters (Evans 2001).

Research on air pollution as a stressor has not examined psychophysiological markers of stress. Understandably most health research on pollutants has focused on respiratory functioning or, in the case of toxins, neurological parameters.

1.2 Cognitive Performance And Learning

Short-term exposure to crowding in the laboratory impairs performance under a limited set of conditions. Performance is degraded only when substantial cognitive load is placed upon the individual, for example by having to monitor multiple signals or to respond to rapid or ambiguous signals (Baum and Paulus 1987). Parallel results have been found for noise (Smith and Jones 1992). Experimental work on pollutants and task performance has primarily been restricted to neurotoxicological testing.

Residential crowding is associated with achievement deficits among school children (Evans et al. 1998, Saegert 1982), and numerous studies have shown associations between chronic noise exposure and reading deficits (Evans and Lepore 1993). The noise studies include some longitudinal evidence, dose-response data, and some work on underlying cognitive processes to account for the findings. Speech perception and language acquisition appear to be negatively impacted by chronic noise exposure. Most of the noise and reading studies ruled out hearing impairment as an alternative explanation.

1.3 Interpersonal Relationships

Crowding induces negative affect, heightens irritability and hostility, and may provoke aggression (Baum and Paulus 1987). Residential crowding is associated with more conflicted family relationships including more corporal punishment (Evans et al. 1998, Saegert 1982). Noise is an irritant that, when coupled with provocation or modeling, can lead to elevated aggression (Cohen and Spacapan 1984). Noise itself does not produce aggression but can amplify hostile reactions already present. Attempts to associate crowding or noise exposure with crime have generally proven unsuccessful. There is also evidence that crowding (Baum and Paulus 1987) and noise exposure (Cohen and Spacapan 1984) can suppress altruism. Perceptible air pollution can increase negative affect and, if not at high levels, elevate aggression (Evans 1994). The nonlinear relation between air pollution levels and aggression may reflect underlying negative affect (Rotton 1983).

1.4 Psychological Health

Given both experimental and field evidence linking environmental stressors to negative affect and conflicted interpersonal relationships, many investigators have endeavored to demonstrate associations between chronic exposure to environmental stressors and mental health. For all three environmental stressors, the data are mixed, although careful scrutiny reveals some consistent patterns. Studies of residential crowding and mental health that have relied upon individual-level data reveal modest relations. Studies of more serious outcome measures of psychiatric impairment as well as those relying on aggregate-level indices of crowding (e.g., people acre) typically find no association with mental health (Evans 2001).

The data on noise and mental health are more equivocal, with no discernable trends, although many studies have used poor estimates of noise exposure and relied upon catastrophic mental health outcome measures (e.g., psychiatric hospitalization). There is some evidence that those who are noise-sensitive, which is related to neuroticism, may be especially vulnerable to elevated psychological distress in relation to noise exposure (Stansfeld 1993). Air pollution exposure may also be related to psychological distress, although not much data have been collected (Evans 1994, Rotton 1983).

1.5 Summary

Acute and chronic exposure to crowding or noise can elevate cardiovascular and neuroendocrine indicators of stress. Insufficient research has examined similar reactions to pollution. Short-term exposure to crowding or noise can impair performance when cognitive load is high. Chronic crowding has been linked to achievement deficits among children in a few studies, and numerous studies have revealed noise-related reading deficits. Crowding, noise, and air pollution, both in the laboratory and under naturalistic conditions, increase annoyance, irritability, and hostility. Aggression may be more likely to occur when prior provocation or modeling of conflict has occurred. In the case of pollution, evidence suggests that the relation is nonlinear and may be mediated by negative affect. Residential crowding and exposure to pollutants appear to be associated with elevated psycho-logical distress. The evidence for mental health sequels of noise exposure is equivocal.

2. Underlying Mechanisms

The initial phase of behavioral research on environ-mental stressors was focused on documenting potential adverse effects on human functioning along with examining possible individual differences in responses. Several reliable gender differences have been uncovered for crowding, suggesting that men react more strongly physiologically, whereas women may suffer stronger negative affective responses. Noise-sensitive individuals tend to react more negatively to noise in a variety or ways in comparison to their less sensitive counterparts. Attempts to identify systematic personality or dispositional differences in reactions to environmental stressors have generally been unsuccessful. The strongest data to date suggest that persons seeking higher levels of arousal or sensation are less adversely affected by crowding and noise (Mahrabian and Russell 1974).

Current research has shifted emphasis, focusing primarily on underlying, explanatory psychosocial processes to help account for the apparently stressful, adverse effects of environmental stressors on human well-being. The two underlying psychosocial processes that have garnered the most attention to date are control and social support.

2.1 Control

Research on all three environmental stressors implicates lack of control as an important component of stress reactions. Two general approaches have led to this conclusion. In the first approach, studies of noise (Cohen et al. 1986), crowding (Baum and Paulus 1987), and air pollution (Rotton 1983) have shown that the negative impacts of each of these stressors are substantially attenuated by providing individuals with a sense of control over the stressor. For example, in a classic set of experiments, Glass and Singer (1972) demonstrated that the negative effects of noise were essentially eliminated if subjects believed they could shut off the noise with a switch. Just the perception of control was sufficient to ameliorate the harmful impacts of noise, regardless of whether subjects actually exercised the control option.

The second approach to examining control as an underlying explanatory process for the stress effects of environmental stressors has been to study motivational deficits associated with learned helplessness among those chronically exposed to environmental stressors. As explained in more detail in the entry Learned Helplessness, repeated exposure to uncontrollable stimuli can lead to decrements in motivation caused by the belief that the outcomes of one’s actions are independent of those actions. Children chronically exposed to noise or to crowding are less likely to persist in their attempts to solve challenging puzzles (Evans 2001). Adults living under more crowded conditions adapt a withdrawal strategy in group game-playing scenarios. Their degree of withdrawal is closely matched by self-reports of feelings of loss of control over the immediate social environment in their residences (Baum et al. 1981). Physiological stress reactions to traffic congestion have also been shown to be partially attributable to diminished perceptions of control (Evans 2001).

2.2 Social Support

Several studies indicate that residential crowding is associated with diminished social support (Evans 2001). This is believed to occur as a consequence of a common coping strategy for dealing with crowding, namely social withdrawal. Long-term crowding appears to precipitate social withdrawal which, in turn, leads to a breakdown of socially supportive relationships in the home. There is also evidence that deteriorated social support mediates the link-age between residential crowding and psychological distress.

Analogous research has not been completed with noise or air pollution, but there are reasons to suspect that similar processes may be operating. Both of these stressors are clearly irritating and can affect one’s propensity for negative social interaction. Further-more, noise interferes with communication, a fundamental building block of socially supportive relationships.

3. Future Directions

From both a methodological and a policy perspective, there is critical need for prospective longitudinal field studies of environmental stressors and human psycho-logical functioning. Ideally these studies will also generate dose-response functions in order to under-stand critical values of environmental stressors for human behavior. At the present we know environ-mental stressors are inimical to optimum psycho-logical functioning, but we cannot say currently precisely how much exposure to a particular stressor is sufficient to produce harm.

Research is likely to continue on underlying processes to explain how and why environmental stressors can interfere with human behavior. Hopefully this kind of research can also incorporate better estimation of human exposure to environmental stressors. Ambulatory monitoring and use of time budget methodologies may prove helpful in this regard.

The contexts in which exposure to environmental stressors occur warrant greater attention. Exposure to environmental stressors is not random. Most of these stressors are experienced jointly (e.g., noise and crowding) and frequently accompany poverty. More psychological analysis of multiple environmental and social stressors exposure is called for.

The social and behavioral sciences will continue to provide insights that expand our understanding of environment and health. Psychological stress provides one theoretical framework that has proven useful for doing so. Our attitudes towards the natural environment, along with models of ecologically responsible behavior, are two additional topics where the social and behavioral sciences are likely to continue making important contributions to the environmental sciences. Human behavior plays a pivotal role both in the etiology of environmental problems and as an index of their impacts.

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