고려대학교 산업공학과 IND641 Engineering Psychology Chapter 12. Stress and Human Error ...

고려대학교 산업공학과

IND641 Engineering Psychology

Chapter 12. Stress and Human Error

STRESS stressors (Fig 12.1) – environmental factors, psychological factors, time pressure

1. produce phenomenological experience – emotional or affective2. physiological change observable, often linked with phenomenological experience3. affect characteristics of information processing, not always degrade performance

Stress Effects on Performance developing models that will accurately predict stress effects is challenging1. ethical considerations make it difficult to carry out controlled experiments2. human performance response to stressors appears to be inconsistent and unpredictable the pattern of inferred human stress response1. stress was a causal factor in the errors made in the events, yet the causal inferences will

always be ambiguous2. there have been a series of efforts to capitalize on stress imposed for other reasons, to gain

insights into performance3. a number of studies have examined that effects of stressors in more controlled laboratory

environments Stress Component Effect

Arousal easiest way to measure the quantitative levels of many stressors is through physiological

measures of arousal – HR, pupil diameter, catacholomine in the blood or urine



associated with improving the level of performance most stressors increase the level of arousal but sleep loss and fatigue will decrease arousalSelective Attention: Narrowing increased selectivity or attentional narrowing results from a wide variety of different stressors usually degrade performance; may actually facilitate performance with focused attentionSelective Attention: Distraction simply impose a distraction, thus divert selective attention away from task–relevant processingWorking-Memory Loss negative effects of anxiety, perceived danger, noise The Yerkes Dodson Law an inverted U-shaped pattern relating stress to human performance (Fig 12.2) at the lower end of the arousal scale, increasing stress by increasing arousal will increase

performance higher levels of arousal, stress begins to produce the attentional and memory difficulties that

cause performance to decrease the optimum level of arousal – greater performance for simple task than complexPerseveration high level of stress will cause people to perseverate or continue with a given action or plan of

action that they have used it in the past combined effects of stress on attentional narrowing and perseveration can contribute to a pattern

of convergent thinking or “cognitive narrowing and tunneling” that can be dangerous in crisis decision making

stress will enhance the confirmation bias



Strategic Control the characterization of a set of strategies that the human will consciously adapt to cope with

the perceived stress effects in Fig 12.3 adaptive closed-loop model of stress -- appraisal and strategic choice operators not respond to the stressor per se, but to the perceived or understood level of

stress (cognitive appraisal) selection of the appropriate or inappropriate strategies -- four major categories of adaptive

responses1. Recruitment of More Resources try harder or acceleration (time stress) – can be adaptive but it has risks

long-term costs of fatigue and possible health risks acceleration may eliminate redundancies confusions and errors shift in the speed-accuracy trade-off, toward faster but more error-prone performance

2. Remove the Stressor3. Change the Goals of the Task people adaptively invoke qualitatively different performance strategies under higher stress

conditions a simpler and less effortful strategy is often chosen people to abandon compensatory strategies in favor of simpler non-compensatory ones, which are simpler, quicker, and require less WM – more stress resistant

humans adapt by choosing a simpler and more efficient strategy stressors even produce performance improvement4. Do Nothing



Moderating EffectsOther Stressors -- one stressor may reduce rather than amplify the effect of anotherPersonality locus of control – those with an internal (self) locus of control are less stressed action-oriented (more proactive and effectively filter less relevant material) vs. state-oriented

(more reactive and more inclined to accelerate performance)Training and Expertise highly skilled operators are more immune or buffered from the negative effects of stress1. automaticity pure expertise in routine performance is not sufficient2. greater repertoire of strategies available3. greater familiarity with the stressors

Stress RemediationEnvironmental SolutionsDesign Solutions -- emergency proceduresTraining

HUMAN ERROR human error is the primary cause of 60 to 90% of major accidents and incidents result of bad system design or bad organizational structure rather than irresponsible action the error was only one of a lengthy and complex chain of breakdowns Categories of Human Error: An Information Processing Approach

errors of commission / errors of omission mistakes, slips, lapses and mode errors (Fig 12.4)



Mistakes failing to formulate the right intentions – shortcomings of perception, memory, cognition knowledge-based mistakes

incorrect plans of actions are arrived at because of a failure to understand the situation (incorrect knowledge) influences of many biases and cognitive limits

insufficient knowledge of expertise to interpret complex information poor displays either present inadequate information or in a poor format

rule-based mistakes operators know the situation, and they invoke a rule or plan of action to deal with it the choice of rule – “if-then” logic choice of a rule guided by frequency and reinforcement

Slips the right intention is incorrectly carried out capture errors – the intended stream of behavior is captured by a similar, well practiced

behavior pattern1. intended action involves a slight departure from the routine, frequently performed action2. either stimulus or action sequence are closely related to now inappropriate action3. action sequence is relatively automated and therefore not monitored by attention

pouring orange juice rather than syrup on the waffles while reading the newspaperLapses failure to carry out any action at all tied to failure of memory – colloquially referred to as forgetfulness occur too frequently in maintenance or installation procedures



Mode errors closely related to slips but also have the memory failure characteristic of lapses pressing the accelerator of a car to start when the transmission is in the “reverse” mode a joint consequence of relatively automated performance or of high workload and of improperly

conceived system designDistinction Between Error Categories the ease of detectability

detection of slips – relatively easy preventing slips – system and task design preventing mistakes – design features related to effective display or on training

Human Reliability Analysis to predict human error (Fig 12.5) technique for human error rate prediction (THERP)

1. Human error probability (HEP) – the ratio of the number of errors made on a particular task to the number of opportunities for errors from databases of actual performance or estimated by experts (heavily biased and not always terribly reliable)

2. event tree or fault tree (Fig 12.6)3. HEPs can be modified by performance shaping factors, multipliers(expertise or the stress)

Lack of DatabaseError MonitoringNonindependence of Human Errors first error resulting frustrations and stresses increase the likelihood of a subsequent error first error increase care and caution make future errors less likely



Integrating Human and Machine Reliabilities to integrate actuarial data of human error with machine data to estimate system reliability –

difficult to justify nonindependence issue a considerable challenge to estimate reliability Errors in the Organizational Context

human error as only one small component in a set of more serious organizational deficiencies local triggers or active failures – the tip of the iceberg resident pathogens or latent conditions – the base of the iceberg (Fig 12.7)

Error RemediationTask DesignEquipment Design1. minimize perceptual confusions2. Make the execution of action and the response of the system visible to the operator3. Use constraints to “lock out” the possibility of errors4. Offer remedies5. Avoiding multimode systemTrainingAssists and Rules memory aids or procedures checklistsError-Tolerant Systems errors are undesirable but inevitable error as the inevitable downside of the valuable flexibility and creativity of the human operator not allow to carry out irreversible actions

고려대학교 산업공학과 IND641 Engineering Psychology Chapter 12. Stress and Human Error ...

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