Cognitive science is a science of intelligence, of knowledge and its uses. Research is psychological theory follows four major themes: Perception, Attention, Memory, and Performance. Only when the range of cognitive mechanisms and functions is known, can possible theoretical approaches characterizing human thought and cognition be distinguished. Advancement in the understanding of psychology becomes evident through a unifying, theoretical approach to cognitive phenomena, and consideration of fundamental processing principles from cognitive science. Several other fundamental concepts have been missing from cognitive studies, including the roles of culture, social interaction, emotions, and motivation. Cognitive scientists should make use of evidence from brain damage and mental illness, on the premise that a system operation can be revealed by the error that such damage causes. (Author/GSK)