Performance
Performance is completion of a task with application of knowledge, skills and abilities. In work place, performance or job performance means good ranking with the hypothesized conception of requirements of a task role, whereas citizenship performance means a set of individual activity/contribution (prosocial organizational behavior) that supports the organizational culture. In the performing arts, a performance generally comprises an event in which a performer or group of performers present one or more works of art to an audience. Usually the performers participate in rehearsals beforehand. An effective performance is determined by competency of the performer - level of skill and knowledge. Spencer and McClelland in 1994 defined competency as "a combination of motives, traits, self-concepts, attitudes, cognitive behavior skills (content knowledge)" that helps a performer to differentiate themselves superior from average performers. A performance may also describe the way in which an actor performs. In a solo capacity, it may also refer to a mime artist, comedian, conjurer, or other entertainer.
Psychology
Psychology is the science of behavior and mind, including conscious and unconscious phenomena, as well as feeling and thought. It is an academic discipline of immense scope and diverse interests that, when taken together, seek an understanding of the emergent properties of brains, and all the variety of epiphenomena they manifest. As a social science it aims to understand individuals and groups by establishing general principles and researching specific cases.
Performance
"For me, the most important thing is the element of chance that is built into a live performance. The very great drawback of recorded sound is the fact that it is always the same. No matter how wonderful a recording is, I know that I couldn't live with it -- even of my own music -- with the same nuances forever."
Aaron Copland, quoted in Classic Essays on Twentieth-Century Music. ISBN 0028645812.
Psychology
Psychology appeared to be a jungle of confusing, conflicting, and arbitrary concepts. These pre-scientific theories doubtless contained insights which still surpass in refinement those depended upon by psychiatrists or psychologists today. But who knows, among the many brilliant ideas offered, which are the true ones? Some will claim that the statements of one theorist are correct, but others will favour the views of another. Then there is no objective way of sorting out the truth except through scientific research.
Raymond Cattell (1965). The Scientific Analysis of Personality, Baltimore, MD: Penguin, p. 14.