This chapter explains what cognitive psychologists have discovered so far about the human attentional system. Cognitive psychology is concerned with the scientific study of how the mind works in receiving, storing and using knowledge in everyday life. Within this field, the study of attention, or the concentration of mental effort on sensory or cognitive events, is extremely important. The chapter identifies three key components of the construct of attention: selectivity of processing, mental time-sharing of actions and regulation of alertness. It reviews the historical treatment of this multi-dimensional construct. Theories of attention comprise both filter and capacity models. In general, filter theories of selective attention are concerned with identifying the location and characteristics of certain structural limitations in the information processing system. Capacity theorists, however, adopt a less mechanical view of attention. The chapter concludes by the proposition the attention may be regarded as a skill which can be enhanced through appropriate practice and instruction.