To carry out effective User Centred Design, designers need to something of how humans process information: how they perceive the world, focus their attention, use memory, make choices and respond. Cognitive psychology is the study of such information processing. Knowing the capabilities and limitations of your users will lead to you making better design choices. This Unit introduces cognitive psychology and deals with one key aspect, namely visual perception – i.e., how we process visual information that is presented to us. You will learn about theories of visual perception and how this knowledge might help build better interactive systems.