Intuitive does not necessarily mean simple, as the tasks are often far from simple. But a person familiar with the basic concept of the action to be performed should easily understand how to use the GUI.

Of course, the user of the toolbox should (ideally) know what she or he wants to do with the data. That means that we can rely on a basic understanding of data analysis specific for the data processed with the toolbox.

On the other hand, often the full complexity of a task gets obvious only when starting to perform it. Therefore, it is often helpful to have a “default” behaviour and a well-chosen “default parameter set” helping the user to get to a preliminary result.

A few ideas helping to design intuitive GUIs:

• Try to think about the different steps and the most intuitive sequence of steps before designing a GUI.
• Test the GUI thorougly with at least a few dozens of (ideally different) datasets.
• Have others test the GUI.