Thinking-aloud Protocol


Applicable stages: design, code, test, and deployment.
Personnel needed for the evaluation:
Usability experts: 1
Software developers: 0
Users: 4
Usability issues covered:
Can be conducted remotely: No Can obtain quantitative data: No


During the course of a usability test, the test users are asked to verbalize their thoughts, feelings, and opinions while interacting with the system. It is very useful in capturing a wide range of cognitive activities. Two variations of thinking-aloud protocol technique are:
Provide the test users with the product to be tested (or a prototype of its interface) and a set of tasks to perform. Ask the test users to perform the tasks using the product, and explain what they're thinking about while working with the product's interface.

Thinking aloud allows testers to understand how the user approaches the interface and what considerations the user keeps in mind when using the interface. If the user expresses that the sequence of steps dictated by the product to accomplish their task goal is different from what they expected, perhaps the interface is convoluted.

Although the main benefit of the thinking aloud protocol is a better understanding of the user's mental model and interaction with the product, there are other benefits as well. For example, the terminology the user uses to express an idea or function should be incorporated into the product design or at least its documentation.


  1. J. Nielsen "Usability Engineering", pp 195-198, Academic Press, 1993.