Divide a task into different pieces The percentage of workload at each point is calculated as the average number of tasks per unit time.
Pros
Intuitive Easy to Understand
Cons
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.
IMPORTANT
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