Concept

A concept is a fundamental unit of cognition that classifies entities and encodes shared features. Concepts make it possible to form and combine ideas, draw inferences, and refer to external objects. They act as the meanings of words and play a central role in many cognitive processes, including perception, memory, and reasoning. Researchers distinguish different types of concepts based on their internal structure, mode of acquisition, and domain. These include simple and complex concepts, learned and innate concepts, concrete and abstract concepts, and natural and logical concepts. The classical theory holds that concepts are essentially definitions, each characterized by fixed rules determining to which entities the concept applies. Prototype theory rejects this outlook, arguing that concept membership depends on similarity to a prototype—a cluster of features typically associated with the category. According to exemplar theory, similarity derives from individual memories of concrete instances rather than a single prototypical summary representation. Theory theory maintains that concepts are embedded in domain-specific theories, while conceptual atomism argues that lexical concepts are separate units without internal structure. Philosophers debate whether concepts are mental representations or abstract objects that exist independently of individual minds. Concept learning is the process of acquiring a new concept, which is required before an individual can use it. Suggested learning mechanisms include associative learning, in which similarities are gradually noticed as learners encounter instances, and hypothesis testing, which involves formulating testable rules. Nativism and empiricism are competing theories about whether there are inborn concepts not learned from experience. Researchers also examine how concept learning develops from childhood to adulthood, how nonhuman animals form concepts, and how computers can model and acquire concepts. Concepts are relevant to many fields, including psychology, philosophy, and linguistics. Inquiry into their nature originated in antiquity and became a central topic in the 20th century as...