Provides the student and researcher with a comprehensive and accessible review of performance, the real world and essential cognitive science theory. Four sections cover both theoretical and practical issues: Section One outlines the perspectives on performance offered by contemporary cognitive science, including information processing and neuroscience perspectives. Section Two presents a multi-levelled view of the performer as biological organism, information-processor and intentional agent. It reviews the development of the cognitive theory of performance through experimental studies and also looks at practical issues such as human error. Section Three reviews the impact of stress factors on performance such as noise, fatigue and illness. Section Four assesses individual and group differences in performance with accounts of ability, personality and ageing.