Microsoft applied for a patent to monitor user's brain waves to understand how good (or bad) their interfaces are. Filed on August 9, 2007, the patent application, #20070185697, describes a method of classifying EEG data in a way that separates the wheat from the chaff. From the patent application:
When studying how humans interact with computing devices, it is desirable to be able to determine the effectiveness of a computer-user interface, i.e., a user interface. A traditional way of determining the effectiveness of a user interface is to present a computer user, i.e., a user, with a task, observe the user as he or she operates the user interface to complete the task, and ask the user questions before, during, and/or after the task is performed. The observed behavior and answers to the questions are characterized and quantified. The quantified results are analyzed to determine the effectiveness of the user interface.Link (via New Scientist)
Cognitive neuroscience techniques can be used to provide a more direct way to determine the effectiveness of user interfaces. A typical cognitive neuroscience technique involves attaching electrical sensors, ie., sensors, to various points on a user's scalp. The sensors are then connected to an electroencephalograph (EEG). One use of an EEG is to sense electrical changes within the brain that correspond to certain brain states. It is possible to determine the effectiveness of a user interface by analyzing a user's brain states before, during, and/or after a user performs a task using the user interface.