WORKLOADEmmanuel SeguiIndustrial/Organizational Psychologist

Workload Overload

Underload Having work that fails to use a worker's

skills and abilities

FLOW (Csikszentmihalyi)

Yerkes-Dodson Law Inverted-U function

• Optimal level of arousal differs for experts/novices and simple/complex tasks.

• Poor performance if too low (low motivation, boredom) or too high (test anxiety)

Work Overload Time-line Model

Time-line model Workload percentage = Time required/Time

available Can have over 100% workload and handle it okay

or less than 100% and not Moderators of time requirement estimations:

Individual differences Level of automaticity Shared vs. separate resources

Work Overload Time-line Model

Definitions of Workload? Physiological and mental demands that

occur while performing a task or a combination of tasks.

Workload is defined as the physical and/or mental requirements associated with a task or a combination of tasks.

Definitions of Workload? Aspect of Interaction between an

operator and an Assigned Task The term workload refers to that portion

of the operators limited capacity actually required to perform a particular Task

Workload Strains Anxiety Physiological reactions

Fatigue Backache Headache Gastrointestinal problems.

Performance Loss

Fatigue One effect of continuous work overload is

fatigue. Fatigue is a stressor that degrades

performance and creates problems in maintaining attention.

Fatigue Fatigue studied in

military operations, long-haul truck drivers, medical workers in hospitals, pilots, ATC (overload)

Fatigue can also result from long periods of doing little (underload).

Examples of the effects of fatigue due to sleep disruption 60% of class A aircraft mishaps in the Air

Force are due to fatigue The explosion of the space shuttle

Challenger is thought to be due to poor decision making of the launch team who received very little sleep prior to their early morning decision to launch the rocket in excessively cold temperature.

Examples of the effects of fatigue due to sleep disruption Over 200,000 auto

accidents per year Medical errors Performance on the

battle field.

Fatigue, Vigilance and Underarousal

Automation may make the problem of underarousal worse.

Workload

Construct Complex phenomenon

Multiple dimensions Hard to define “There is still no universally

accepted definition for mental workload”

Why Measure Workload?

Avoid Accidents Performance limits Predict top performance and operation

failure

Why Measure Workload?

“If workload is only studied in an experimental environment and is not applied to real-life situations, then the research is useless. It is easy to get a count of eye blinks per minute, but applying that to exactly how much workload a pilot flying a bombing mission is experiencing may be quite difficult. This difficult task is essentially the most important aspect of workload because it is the reason workload is studied”

Measuring Workload 3 main classifications

Performance-based measures Physiological measures Subjective measures

Performance-based measures Primary task measures Secondary task

methods Measure the reserve

capacity left over after performing the primary task (examples: memory tasks, mental arithmetic)

Performance-based measures Advantages

Non-invasive and non-interfering

Tracks changes in workload dynamically. (i.e., as performance proceeds)

Disadvantages Unable to predict

failure

2. Physiological measures Physiological

measures Heart rate Blink rate EEG Pupil diameter

Visual Scanning Used extensively in aviation research

gaze characteristics on cockpit instruments mean dwell time of each fixation on the pilot's primary

instrument Tole, et al. (1982)

Visual scanning behavior and mental workload in aircraft pilots scanning behavior was also a function of the estimated

skill level of the pilots, with novices being affected by the loading task much more than experts.

Visual scanning of instruments in a controlled task may be an indicator of both workload and skill

ECG Bonner & Wilson

(2001) Monitored pilots

throughout test and evaluation of an aircraft

Note differences between subjective workload and HR

Physiological Measures Advantage

Discreet Disadvantage

Expensive

3. Subjective measures The NASA Task Load Index

(NASA-TLX) multidimensional assessment tool that rates perceived workload

Temporal Demand, Effort, Stress, Own Performance, Frustration, Physical Demand (6 sources of workload)

3. Subjective measures SWAT Developed by US

Air Force (Subjective Workload Assessment Technique) Time, effort, stress

(sources of worlkload)

3. Subjective measures Advantage

Easy to do High Face validity

Disadvantage Bias

Recap

Remediation Task redesign or assignment to multiple workers Automate Develop display design that highlights the most

important information. Training for high time-stress workload situations. Training of task management skills

https://www.youtube.com/watch?v=4HWYVrTbnw0

ANY QUESTIONS?