Workload Assessment

Learn how operators percieve the amount of work they need to perform

What is workload?

Humans have limited attentional resources to process information. Given these limits, workload that is too high can result in performance challenges such as errors, lapses, slower response times. On the other hand, workload that is too low can also contribute to poor concentration and loss of situational awareness.  

What is workload assessment and when should it be used?

Workload assessment is an evaluation of how much demand is put on the different types of attentional resources (cognitive, perceptual, motor, etc.). If more than one task draws upon the same resource, performance decrement will occur. 

Workload assessment can be used to determine if an operator is over-burdened or under-burdened, whether resources exist for additional tasks, how personnel can deal with unanticipated situations such as emergencies and incidents.  Results may may point to the need for additional staff or support with technologies and other decision aids.

In situations where new work processes, technologies, or systems are being introduced; or there are changes to roles/responsibilities – workload assessment should be used. 

How to assess workload 

There are multiple ways of measuring workload, each with its own advantages and disadvantages. 

Subjective: Instruments such as NASA-TLX (Task Load Index) and SWAT (Subjective Workload Assessment Technique) ask operators to report their perceived workload. There are several advantages of using these instruments: ease of use, validated scales, low cost. The disadvantage is that the instruments ask people to report on their own workload, which may not be very reliable and does not capture actual task performance.

Objective:  A secondary task can be used to objectively measure workload. A subject is asked to perform a second task (such as tapping a finger)  in addition to a primary task (such as steering). Poorer secondary task performance (e.g., skipping finger taps) indicates heavier attention demands. This is a fairly reliable method to capture workload, but needs to be done in an experimental setting.

Physiological: Workload has also been captured using physiological measures such as measuring heart rate, pupil response, and brain wave activity via electroencephalogram (EEG), . These approaches are common in aviation and require specialized equipment.

For more on Workload Assessment, see: 

Hart, S. G. & Staveland, L. E. (1988) Development of NASA-TLX (Task Load Index): Results of empirical and theoretical research. In P. A. Hancock and N. Meshkati (Eds.) Human Mental Workload. Amsterdam: North Holland Press.

Rubio, S., Diaz, E., Martin, J., Puente, J. M. (2004). Evaluation of subjective mental workload: A comparison of SWAT, NASA-TLX, and workload profile methods. Applied Psychology: An International Review, 53(1), 63-86.

Wickens, C.D. (1984). Processing resources in attention, in R. Parasuraman & D.R. Davies (Eds.), Varieties of attention, (pp. 63–102). New York: Academic Press.