Posted on: September 10, 2020
We have all experienced stress at some point in our lives. Stress is typically seen as an emotional state of heightened arousal that can impair performance and, if severe enough, potentially disrupt behaviour and have negative consequences for health. Stress is not always negative, however, for it may also serve as an energizing force that motivates people to perform well. Distinguishing the conditions under which stress impairs cognition and performance, and the mechanisms by which it does so, is one of the many challenges of stress research. Knowing how stress degrades human performance can help to support the design of more stress tolerant interfaces, or to develop stress reducing training techniques. Below we’ll look at the effects brought on by stressors, and remediation solutions to help minimize the degrading effects of stress on human performance.
Stress Component Effects
Selective Attention: Narrowing
Changes in human selective and focused attention, mediate many stress effects. One of the most important and robust of these appears to be an increased selectivity or attentional narrowing that results from a wide variety of different stressors. The stress effect on tunnelling is not simply defined by a reduction of the spatial area of the attention spotlight, so that peripheral stimuli are automatically filtered. Rather the filtering effect seems to be defined by subjective importance, or priority, as when skimming text under time stress. Performance of those tasks of greatest subjective importance remain unaffected—or perhaps enhanced (through arousal)—in their processing, whereas those of lower priority are filtered.
Selective Attention: Distraction
Many stressors simply impose a distraction and thus divert selective attention away from task-relevant processing. Loud or intermittent noises or even the conversation at a nearby table at the library will serve as a source of such distraction. It also appears to be the case that the documented influence of life stress events (like family or financial problems) at the workplace relates to the distraction or diversion of attention to thinking about these issues, at the expense of processing job related information.
Working Memory Loss
Several researchers have directly identified the negative effects of anxiety stress on working memory. Noise, as well as danger and anxiety, will also degrade working memory. The stress effects of noise on working memory can be seen to result from either of two causes. First, it is clear that noise will disrupt the “inner speech” necessary to carry out rehearsal of verbal information in the phonetic loop, because rehearsal is a resource-limited process. Second, both noise and non-noise stressors can distract or divert attention away from rehearsal of material that is either phonetic or spatial, in a way that will allow the representation of that information to degrade.
There is evidence that high levels of stress will cause people to “perseverate” or continue with a given action or plan of action that they have used in the past. For example, in problem solving under stress people will be more likely to continue trying the same unsuccessful solution (the very failure of which might be a cause of increasing stress). The concept of perseveration with previous action patterns is also consistent with the view that, under stress, familiar behaviour is little hampered, but more novel behaviour becomes disrupted, an effect that has profound implications for the design of procedures to be used under the stressful conditions of emergency.
It is apparent that the combined effects of stress on attentional narrowing and perseveration can contribute to a pattern of convergent thinking or “cognitive narrowing” that can be dangerous in crisis decision making, stress will initially narrow the set of cues processed to those that are perceived to be most important; as these cues are viewed to support one hypothesis, the decision maker will perseverate to consider only that hypothesis, and will process the (restricted) range of cues consistent with that set. That is, stress will enhance the confirmation bias, causing the decision maker to be even less likely to consider the information that might support an alternative hypothesis.
Perhaps the most important processing changes that occur under stress can be characterized by the general label of strategic control: that is, the characterization of a set of strategies that the human will consciously adapt to cope with the perceived stress effects. These include:
- Recruitment of more resources: Here the response is simply to “try harder,” or mobilize more resources in the face of the stressor. If the source of stress is time pressure, then this strategy may be labelled as “acceleration”: doing more in less time.
- Remove the stressor: The human may sometimes adapt successfully by simply trying to eliminate the source of stress. At times this is easy, such as turning off (or removing oneself from) a stressful source of noise, postponing performance of a task till a time in which one is no longer sleep deprived or postponing a deadline to remove time pressure. At other times, removal may be more difficult, such a putting a source of anxiety out of mind and may depend upon the availability of trained stress coping skills.
- Change the goal of the task: Stress researchers have revealed a variety of ways in which people adaptively display qualitatively different performance strategies under higher stress conditions. What makes these strategies adaptive is that they are chosen to be ones that are more immune to the known degrading effects of stress on information processing. Hence a simpler, less effortful strategy is often chosen. The skilled operator will often have available a repertoire of such strategies, to be able to choose the one that is most immune from stress effects. It is for this reason, in part, that stressors sometimes fail to produce performance decrements: humans adapt by choosing a simpler and more efficient strategy. Indeed, sometimes stressors even produce performance improvements.
The final strategy identified is for people to simply do nothing to adjust their processing under stress, allowing the stress effects to influence performance in a more predictable way.
A variety of techniques may be adopted in the effort to minimize the degrading effects of stress on human performance. Roughly these may be categorized as environmental solutions, design solutions, which address the task, and personal solutions, which address the operator, either through task training or through training of stress management strategies.
Clearly, where possible, stressors should be removed from the environment, a solution that is more feasible in the case of external stressors, such as noise or temperature, than for internal stressors such as those related to anxiety.
Design solutions may focus on the human factors of displays. If perceptual narrowing among information sources or unsystematic scanning does occur, then reducing the amount of unnecessary information (visual clutter) and increasing its organization will somewhat buffer the degrading effects of stress. Any design efforts that minimize the need for operators to maintain or transform information in working memory should be effective. Thus, high display compatibility, either with responses or with the mental model of the task, is important.
Programs of stress inoculation training or stress exposure training have been designed to introduce humans to the consequences of stress on their performance. Such programs provide a mixture of explanation of anticipated stress effects, teaching of stress coping strategies, and actual experience of stressors on performance, an experience that is gradually introduced and adaptively increased. It is apparent that prediction of the effects of stressors on performance remains one of the greatest challenges for human performance theory, a consequence of the multidimensional effects of stress, and the multiple compensatory or coping strategies available to people. These must be revealed by looking beyond the final output of task performance to consider the behaviour and cognitive processes involved in that performance, as well as physiological reflections of coping strategies. However, the very availability of those strategies, which can make precise performance prediction difficult for engineering psychology serves as a real benefit for human factors by making available several options for effective remediation, through training and design.
This blog is an excerpt of Chapter 11 Mental Workload, Stress, and Individual Differences: Cognitive and Neuroergonomic Perspectives from the book Engineering Psychology and Human Performance, 4th Edition by Christopher D. Wickens, Justin G. Hollands, Simon Banbury, Raja Parasuraman