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Verbal Protocol Analysis

Learn from operators they they are thinking about while performing tasks

A man conducting a train.
Photo Source:; Photographer Paolo Bona

Verbal Protocol Analysis can be used to understand how the operator perceives, operates, or uses a system, product, or space. Also known as the “think aloud” method, the researcher asks an individual to say all thoughts and perceptions that occur while performing a task.  Gaining insight into an individual’s mental model provides insights into what the individual is noticing and attending to while performing an activity.   

Verbal Protocol Analysis can be used to learn meaningful information on a variety of topics.  For example, it can reveal strategies that an individual uses in order to maintain consistent performance during an event -- such as what he or she is paying attention to while negotiating a switch or intersection.  It can also be used to understand the adaptations and workarounds the operator needs to perform to conduct his/her work safely and efficiently.

The think aloud method can be used while conducting field observations of operators and/or during usability assessments of new technology. The method can also be used in tandem with video or other kinds of recordings after an event so that the operator can describe what was happening and what they were thinking as the event occurred (Nemeth, 2004).

Benefits and Drawbacks of Verbal Protocol Analysis

  • An advantage of verbal protocol analysis is that it can allow investigators to obtain insight into operators’ mental models, strategies for accomplishing tasks, and concerns and difficulties as they are performing a task real-time.
  • A drawback is that individuals who are less verbal may have difficulty articulating their thought processes sufficiently. 
  • In addition, thinking aloud while conducting a task can be distracting and disruptive for some operators. This can inhibit the investigator from gaining an accurate picture of the operators’ thought processes and perceptions.
  • It is important that Investigators recognize both the benefits and limitations of verbal protocol analysis, and use it in conjunction with other methods so that findings can be triangulated.

For more information on Verbal Protocol Analysis, see:

  • Ericsson, K., & Simon, H. (May 1980). "Verbal reports as data".Psychological Review 87 (3): 215–251.
  • Ericsson, K., & Simon, H. (1993). Protocol Analysis: Verbal Reports as Data   (2nd ed.). Boston: MIT Press
  • Nemeth, C (2004). Human factors methods for design. Boca Raton, FL: Taylor and Francis/CRC Press