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Thinking Aloud Protocol 

What is it?

Thinking Aloud protocol is a popular technique used during usability testing. During the course of a test, where the participant is performing a task as part of a user scenario, you ask the participant to vocalize his or her thoughts, feelings, and opinions while interacting with the product.

How do I do it?

You begin by providing your participant with the product to be tested (or a prototype of its interface) and a scenario of tasks to perform. Ask participants to perform the tasks using the product, and explain what they're thinking about while working with the product's interface.

Thinking aloud allows you 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, you can gain 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.

When should I use this technique?

Use this technique in any stage of development. Thinking aloud is a cheap way of getting a lot of good qualitative feedback during testing.

Who can tell me more?

Click on any of the following links for more information:

Dumas, JS, and Redish, Janice, A Practical Guide to Usability Testing, 1993, Ablex, Norwood, NJ, ISBN 0-89391-991-8 (paper)

Lindgaard, G., Usability Testing and System Evaluation: A Guide for Designing Useful Computer Systems, 1994, Chapman and Hall, London, U.K.  ISBN 0-412-46100-5

Nielsen, Jakob, "Guerrilla HCI: Using Discount Usability Engineering to Penetrate the Intimidation Barrier," online Web page at

Rubin, Jeffrey, Handbook of Usability Testing, 1994, John Wiley and Sons, New York, NY
ISBN 0-471-59403-2 (paper)


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