The cognitive walkthrough is a method of discount ("quick and dirty") usability testing requiring several expert evaluators. A set of appropriate or characteristic tasks to be completed is compiled. The evaluators then "walk" through each task, noting down problems or difficulties as they go.
Since cognitive walkthroughs are often applied very early in development, the evaluators will often be working with mockups of interfaces such as paper prototypes and role-playing the part of a typical user. This is made much simpler if user personas, detailed descriptions of fictitious users, have been developed, because these simplify the role-playing element of cognitive walkthrough. These are often developed at the beginning of a user-centred design process, because designers often find it much easier to design to the needs of a specific user.
Evaluators are typically experts such as usability specialists, but the same basic technique can also be applied successfully in many different situations.
Once you have a relatively detailed prototype, paper or otherwise, you are ready to try a cognitive walkthrough.
Start off by listing the tasks that you expect users to be able to perform using your Web site or program. To do this, think about the possible uses of the site; perhaps you are expecting users to be able to book rooms or organise tours, or find out what events your organisation is running in the next month, or find opening times and contact details for your organisation. Write down each of these tasks.
Secondly, separate these tasks into two parts: the user's purpose (their intention) and the goals that they must achieve in order to complete this. Take the example of organising a tour; the user begins with the purpose of finding out what tours are available. In order to achieve this, they look for a link on your Web site leading to a Web page detailing possible tours. Having chosen a tour, they gain a new purpose - organising a tour date - and a new set of goals, such as finding a Web page that lets them book a tour date and filling it out appropriately.
Separating tasks into tiny steps in this way is known as decomposition, and it is mostly helpful because it allows you to see exactly where and when the interface fails to work with the user's expectations. It is important to do this in advance, because otherwise you find yourself evaluating your own trial-and-error exploration of the interface! Following these steps "wearing the users' shoes" by trying out each step on a prototype version of the interface shows you where the user might reach an impasse or a roadblock and have to retrace his or her steps to get back on track. As a result, you will gain a good idea of places where the interface could be made simpler or organised in a more appropriate manner.
To help this process, a Walkthrough Evaluation Sheet is filled in for each step taken. An example is shown below :
Cognitive walkthroughs are often very good at identifying certain classes of problems with a Web site, especially showing how easy or difficult a system is to learn or explore effectively - how difficult it will be to start using that system without reading the documentation, and how many false moves will be made in the meantime.
The downside is principally that on larger or more complex tasks they can sometimes be time-consuming to perform, so the technique is often used in some altered form. For example, instead of filling out an evaluation sheet at each step, the evaluation can be recorded on video ; the evaluator can then verbally explain the actions at each step.
'Cognitive walkthroughs are helpful in picking out interface problems at an early stage, and works particularly well together with a user-centred design approach and the development of user personas. However, the approach can sometimes be time-consuming, and since reorganising the interface is often expensive and difficult at later stages in development, the cognitive walkthrough is usually applied early in development.