Unit 4 introduced the area of cognitive psychology and focused on the important cognitive process of visual perception. Although vision is, at present, the key sense used in interaction, there are and will be roles for our other �input channels�. This unit looks at the user�s capabilities and limitations in terms of the auditory (hearing) and haptic (touch) senses and also, more briefly, at the possibilities of using taste and smell in interaction. Technologies and applications relevant to the different channels will be discussed. The unit continues with an exploration of two other cognitive elements: the process of attention and human memory. You will learn about these elements and, importantly, how this knowledge can be applied in the design process.