Mental Workload What is Mental Workload Why measure

Mental Workload

What is Mental Workload? • Why measure it? – Performance limits – Predict top performance • Tasks – Cognitive/perceptual – multiple

What kind of tasks have High mental workload? • • • High Air traffic control Pilot Military command & control Nuclear power plant operator anesthesiologist • • N/A Computer programmer College professor Mathematician Technical writer

Key Elements for High mental workload tasks • • Stimulus driven not self paced Large fluctuations in demand Multiple simultaneous tasks High stress/High consequence

Workload & Arousal Yerkes-Dobson law Low arousal Low performance Moderate arousal High performance Over arousal Low performance

Basic approaches to measuring mental workload • Analytic – Task difficulty – Number of simultaneous tasks • Task performance – Primary task – Secondary task • Physiological (arousal/effort) • Subjective assessment

Analytic Models • Tracking models predict based on systems dynamics • Queuing models predict on the basis of task co-occurrence • SAINT / micro. SAINT best developed queuing models

Resources/Attention • Some limited capacity – Unitary: task always depletes common pool by a constant amount – Multiple: task depletes pools of resources to varying degrees – Mixed: cost of sharing even for highly dissimilar resources

Simplified HIP Model S E N S O Attention Working Memory Y S O R E Term Memory R T Long Unconscious/Automatic Processes

Physiological Measures • heart rate: sinus arrhythmia • blood pressure • respiratory rate variability • tidal volume • ventilation • galvanic skin response • evoked response amplitude • evoked response latency • • evoked response latency electroencehpalogram, spectral components time domain, flicker fusion frequency pupil diameter electromyograms electrooculograms

Subjective Workload Measures • Cooper-Harris – Manual control characteristics • SWAT – Dimension based instrument • NASA – 6 -D assessment scales