Patterns of Stressor Impairment

The central approach to the understanding of stress effects presented in this article focuses on the problem of managing the general threat to task goals through adaptive changes in behavior. However, as I mentioned earlier, different stressors also appear to pose specific threats for tasks, depending on their information processing requirements.

An analysis of stress effects on performance carried out in the 1980s found specific patterns of decrement across different indicators of performance and strategy. Some stressors were more likely to impairs performance on one kind of task and others on a different kind. For example, loud noise typically impairs performance on tasks that require accuracy, short-term memory (STM), or problem solving. Sleep deprivation causes impairment on tasks that require accuracy, speed, and a high level of selective attention, as well as having more general effects on memory.

Both noise and sleep deprivation have effects that are more pronounced under fatigue conditions (when tasks involve long periods of work without breaks). Working in hot conditions has widespread effects on most aspects of performance, especially tasks involving more complex decision making. The effects are related to the exposure time and effective temperature, but, unlike noise, do not appear to increase with time at work.

The set of indicators used in this analysis included general alertness, selectivity of attention, speed versus accuracy, and STM. With changes in cognitive theory over the intervening period and the experience of the effects in real work tasks, some changes to this list are needed. General alertness no longer appears to have strong diagnostic value because it is likely to be involved in all active regulatory behavior.

The mechanisms underlying STM have undergone considerable evolution with the development of working memory (WM) theory by Baddeley and colleagues. In addition, there is a need for a new analysis, which takes into account differential effects of regulatory activity. However, even with these caveats, changes in these performance indicators may be seen as a profile of the sorts of information-processing problems that different stress conditions may give rise to.

The most general pattern of decrement is associated with environmental factors, such as noise, danger, or social evaluation, that give rise to subjective states of threat or anxiety. This may be regarded as the modal stress pattern involving a subjective state of high activation, high selectivity of attention, a preference for speed over accuracy, and reduced WM function.

Decrements are more common on tasks of long duration, especially where the continued use of WM is central to maintaining the flow of the work. Selective attention is normally very effective, unless response is required to a number of different events or subtasks, in which case only the most important may be maintained.

A familiar effect of such stressors is narrowed attention, in which the high-priority features of tasks are maintained and secondary aspects are neglected. Such an effect has been observed for a wide range of stress states, including noise, high workload, threat of shock, danger, and most forms of induced anxiety.

Other stressors are associated with different kinds of changes. For example, WM appears relatively stable under hot working conditions or with extended work periods. In all cases, however, it has become clear that we cannot separate the underlying effects on cognitive processes from those relating to changes in performance goals or strategies.

An increase in reliance on one kind of process may be the result of a strategic reduction in the use of another. Because of this, patterns of stressor effects cannot be discussed without reference to an understanding of what the performer is trying to do when carrying out a task and of what conflicts exist between different goals.