Mental Workload Measurements
Mental Workload Measurements
Determine how mentally demanding a task is. 
Time Line Method
Divide a task into different pieces
The percentage of workload at each point is calculated as the average number of tasks per unit time. 
Easy to Understand
Only pays attention to time
- does not take into account difficulty or stress level
Primary Task Method
Using performance to determine mental workload: 
  • If performance is good, workload is low
  • If performance is bad, workload is high
Not Accurate
Could be attributed to other factors
Measures performance, and not workload
Solution: Secondary Task Method
If you have a tough primary task, secondary task doesn't perform as well.
Secondary task should tap into the same resources as the primary task
Types of Evaluation Methods
1. Sensitive: The one that is most reflective of change
2. Diagnostic: How to tell what resource primary task is using -> try different kinds of secondary tasks. 
Physiological Indicators
  • Blinking/Blink Rate
  • EEG (electroencephalogram)
     - measures brain waves
Heart Rate vs. Heart Rate Variabilty
Heart Rate Variability is better measure.
  • HR Var: Standard deviation of Heart Rate (HR is just mean)
HR Var and Workload
Variability goes DOWN when workload goes UP

ex. Heart rate is more regular when you take an exam. 
Levels of Mental Workload
High Mental Workload
  • Mental Fatigue
Low Mental Workload
  • Boredom or vigilance
  • Ex. Some control room monitoring quality inspection
Extremes are not necessarily good!!
How to deal with Boredom/Vigilance
  • Environment Design (lighting, temperature, noise/sound/music)
  • Work-Rest Cycle
  • Employee Job Rotation
  • Employee Selection and personality
  • Employee Training (most expensive but most important)
Demand Checklist
  • Legibility
  • Visual Search Demand
  • Display Organization
  • Compatibility (Display compatible with mental model)
  • Consistency of Format
  • # of modes of operation
  • Prediction Requirements
  • Mental Rotation
Subjective Methods
Survey (Ask them!)
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