Observation of people interacting with a device to perform a task provides a way of capturing data on errors and performance time as well as providing some insight into the ease or difficulty with which the task is performed (Baber and Stanton, 1996; Stanton, 1999; Stanton and Young, 1999). There are many and varied observational techniques, which fall into three broad categories: direct, indirect, and participant observation (Drury, 1995). Ideally, the participants would be representative end users of the system being analyzed, but this is not always possible.