Cognitive science is the interdisciplinary study of cognition. Cognition includes mental states and processes such as thinking, reasoning, remembering, language understanding and generation, visual perception, learning, consciousness, emotions, etc. Some cognitive scientists limit their study to human cognition, though most consider cognition independently of its implementation in humans or computers: ``cognition, be it real or abstract, human or machine'' (Norman 1981b: 1). Some cognitive scientists study cognition independently of the cognitive agent's environment (cf. Jerry Fodor's ``methodological solipsism'' (1980)); others study it ``within the context of the person, the society, the culture'' (Norman 1981b: 1).
In contrast to this ``definition by intension'', cognitive science can also be defined ``extensionally'' as, roughly, the (hopefully non-empty) intersection of the disciplines of computer science (especially artificial intelligence), linguistics, philosophy (especially philosophy of mind and philosophy of language), and psychology (especially cognitive psychology). Some writers on cognitive science add cognitive anthropology to this list, and most would add the cognitive neurosciences. The former deals in part with the societal and cultural context mentioned above. The latter is concerned with the ``implementation'' of mind in human physiology. Whether one views cognitive science ``intensionally'' as the science of mind or ``extensionally'' as a list of disciplines, it contrasts with other academic disciplines, in which (usually) a common methodology is brought to bear on a multitude of problems: In cognitive science, many different methodologies--those of the several cognitive sciences in the ``extensional'' definition--are brought to bear on a common problem: the nature of ``intelligent cognitive behavior'' (Norman 1981b: 1).
Cognitive science's approach to the study of mind is often contrasted with that of behaviorism. The behaviorist approach to psychology seeks to describe and predict human behavior in terms of stimulus-response correlations, with no mention of unobservable (hence, ``unscientific'') mental states (including mental constructs such as symbols, ideas, or schemata) or mental processes (such as thinking, planning, etc.) that might mediate these correlations (cf. Gardner 1985: 11). A behaviorist who would be willing even to talk about the ``mind'' would view it as a ``black box'' that could only be understood--to use computational jargon--in terms of its input-output behavior. Cognitive science in general (and cognitive psychology in particular) seeks to understand human cognitive functions in terms of mental states and processes, i.e., (to use computational jargon again) in terms of the algorithms that mediate between input and output. (Nonetheless, insofar as behaviorism is concerned with the ``intelligent cognitive'' behaviors listed above, it, too, is a cognitive science.)