This disclosure concerns the monitoring of a user performing tasks. A processor receives multiple consecutive images of an eye of the user captured over a period of time. In each of the multiple consecutive images the processor determines a value representing an eye feature to obtain multiple consecutive values. Based on these multiple consecutive values the processor determines a measure of change that characterises change of the eye feature over the multiple consecutive images. Finally, the processor determines whether the user transitioned from a first task to a second task during the period of time based on the measure of change. The determination of task transitions is robust and efficiently achievable with low-cost equipment, such as web-cameras. The disclosed method is independent of the users environment and therefore particularly applicable where no further devices, such as electronic displays, are used in the users environment.