a method of calibrating the eye gaze direction of a user , the method including the steps of : monitoring a user &# 39 ; s eye gaze direction whilst carrying out a series of predetermined tasks , each of the tasks having an expected subject gaze direction ; and correlating the user &# 39 ; s eye gaze direction with the expected direction for a statistically significant period of time ; calculating , from the correlating step , a series of likely eye gaze direction usage parameters associated with the user .