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HCI Lecture 5

Think-Aloud Protocols

The details of this lecture are available on pages 12-14 of the handout.

Useful Links (under construction)


The main points to be addressed in this lecture were:

What is a think-aloud protocol?

Think aloud protocols consist of observing a user working with an interface while encouraging them to "think-aloud"; to say what they are thinking and wondering at each moment. Think-aloud protocols are of particular value because they focus on the problems a user has; when the user is working without difficulty, direct observation (and hence the think-aloud protocol itself) is of very limited use. This is because the user is unable to communicate as fast as they think and act, unless a specific problem arises which slows them down. It is at these times when this method really shines as it allows the observer to correlate the actions and statements of the participant.

We see the main advantages of this method as:

Furthermore, the protocol may be used in two distinct scenarios.
  1. The observer specifies a definite task to be accomplished by the subject.
    • This allows the observer to concentrate on a specific task they are interested in.

  2. 'Open-ended'; no task is specified, and the user is free to choose their own task.
    • Allows the observer to concentrate on naturally occurring problems

In what way(s) can their usefulness be optimised?

This may be answered by giving an overview of how a think-aloud protocol should be conducted in practice, in order for its results to be realistic and helpful to the observer. The purpose of the experiment, e.g. to examine in detail a specific 'corner' of the interface, or to gain an outline of its general efficacy, should of course be decided upon initially. This will allow the observer to choose one of the scenarios given above, and to tailor the protocol accordingly.


As an observer, you need to make sure of the following:

Note taking
Use of video recording equipment

Use of Prompts

There is a considerable difference between prompting and biasing the user, basically say as much as necessary to keep user happy without helping and making suggestions. Such questions may include:
If a subject is completely stuck a decision may have to be made as to whether to help the participant or not. It is up to the judgement of the observer, but if a decision is made to allow some help the following should be noted:
All of the above maximise the effectiveness of the experiment by noting the effect of your input.


Usually done informally at the time by careful note taking but a more quantitative content analysis can be done by examining video evidence after the experiment.


The method is informal and the most effective single way to maximise effectiveness is to create an informal atmosphere.This is where the subject can feel relaxed and as unaware as possible that their actions are being recorded. As mentioned above hints may well contribute to such an informal atmosphere.


The Think-Aloud Protocol is a very perceptive and informative method and when used effectively can result in a lot of information, regarding an interface etc., being discovered that might not otherwise have been. It is however noting that there are many ways to lessen its effectiveness and it is expensive in investigator and subject time.

This page was created by Angus Beaton, Steven Nicholson, Neil Halliday & Keith Thomas