Stress and WorkloadStress and Workload

Chapter 13Chapter 13

Overview of StressorsOverview of Stressors

PsychologicalPsychological

Threat Threat AnxietyAnxiety FatigueFatigue Frustration Frustration AngerAnger

EnvironmentEnvironment

NoiseNoise HeatHeat ColdCold VibrationVibration Dim lightingDim lighting

Stressor EffectsStressor Effects

Environmental Environmental StressorsStressors Motion StressMotion Stress

– Vibration – VWF & precision effectsVibration – VWF & precision effects– Motion Sickness – decoupling between visual & Motion Sickness – decoupling between visual &

vestibular inputsvestibular inputs Thermal StressThermal Stress

– Normal hot & cold (between 79F & 73F in summer and Normal hot & cold (between 79F & 73F in summer and between 75F & 68F in winter). Assumes 60% humidity between 75F & 68F in winter). Assumes 60% humidity at higher temp and 85% humidity at lower temp.at higher temp and 85% humidity at lower temp.

– Three moderating factors – body temperature, air Three moderating factors – body temperature, air movement, and metabolic activity.movement, and metabolic activity.

Air QualityAir Quality

Psychological Psychological StressorsStressors

Cognitive Appraisal – Awareness of situationCognitive Appraisal – Awareness of situation Level of Arousal – Level of concern for situation which Level of Arousal – Level of concern for situation which

depends on accurate appraisal and skill for dealing depends on accurate appraisal and skill for dealing with situationwith situation

Performance Changes with Over-arousal – make more Performance Changes with Over-arousal – make more mistakes, unsafe actions, lower productivity, poor mistakes, unsafe actions, lower productivity, poor judgmentjudgment

Remediation of Psychological Stress – Simplify Remediation of Psychological Stress – Simplify situational elements, actions to be taken based as situational elements, actions to be taken based as little as possible on working memory, specific training, little as possible on working memory, specific training, & generic emergency stress management training& generic emergency stress management training

Life StressLife Stress

Poor working conditions, Poor working conditions, inequitable wages, personal inequitable wages, personal situations such as death, illness, situations such as death, illness, financial, relationships, etc.financial, relationships, etc.

All can lead to distractions, All can lead to distractions, inattention, and poor productivity.inattention, and poor productivity.

Work Overload, Under-Work Overload, Under-load, & Sleep load, & Sleep DisruptionsDisruptions

Time Line ModelTime Line Model

Task VariabilityTask Variability

Time Stress EffectsTime Stress Effects

RemediationRemediation

Task redesignTask redesign Assign some tasks to co-workersAssign some tasks to co-workers AutomationAutomation TrainingTraining

– Training on component tasks to Training on component tasks to decrease completion timesdecrease completion times

– Training on task management skillsTraining on task management skills

Other RemediationOther Remediation

Mental Workload Mental Workload MeasurementMeasurement

Primary Task Measures – Primary Task Measures – speed & accuracy of speed & accuracy of performanceperformance

Secondary Task Measures Secondary Task Measures - - Measure of reserve Measure of reserve capacity. Assumes performance of primary tasks have capacity. Assumes performance of primary tasks have reserve capacity which allows concurrent performance reserve capacity which allows concurrent performance of secondary tasks. of secondary tasks.

Psychological Measures Psychological Measures - - heart rate variabilityheart rate variability Subjective Measures - Subjective Measures - asking operator to rateasking operator to rate

Workload Dissociations Workload Dissociations – – sometimes primary task sometimes primary task performance will improve, but other workload performance will improve, but other workload measures will increasemeasures will increase

Mental Workload Mental Workload EffectsEffects High mental workload – fatigueHigh mental workload – fatigue Vigilance & under-arousalVigilance & under-arousal

– TimeTime– Event salienceEvent salience– Signal rateSignal rate– Arousal levelArousal level– Remediation – signal enhancement Remediation – signal enhancement

or generating false signalsor generating false signals

Sleep DeprivationSleep Deprivation Not enough sleep – Not enough sleep –

– Staying up to late the night beforeStaying up to late the night before– Long work shiftsLong work shifts– Inability to sleep wellInability to sleep well– Remediation – Remediation – get more sleep or power get more sleep or power

napsnaps Disrupted Disrupted circadian rhythmscircadian rhythms

– Constant shift changesConstant shift changes– Jet lagJet lag– Remediation – Remediation – make periods between make periods between

shift changes longershift changes longer

Performance Measures Performance Measures Over One 24 hr Circadian Over One 24 hr Circadian CycleCycle

DesynchronizationDesynchronization

Shift Work – strategiesShift Work – strategies– Assign workers permanently to a shiftAssign workers permanently to a shift– Assign workers to random shifts (ship watch)Assign workers to random shifts (ship watch)– Rotate shifts on 14 – 21 day schedule (best)Rotate shifts on 14 – 21 day schedule (best)

Jet LagJet Lag– Worse for east bound flightsWorse for east bound flights– Remediation – try to wait until local bed-time Remediation – try to wait until local bed-time

(west bound) or expose yourself to intense (west bound) or expose yourself to intense light until local bed-time (east bound)light until local bed-time (east bound)

Jet LagJet Lag