In cognitive psychology, a basic-level category is a family of events, objects, patterns, emotions, spatial relationships, or social relationships that are cognitively basic. "Dog", "chair", "ball", and "cup" are examples of basic-level categories. Basic-level categories share a variety of properties with one another. Among other similarities, they are the level first named and understood by children, the level with the shortest primary lexemes, the first level to enter the lexicon of a language, the level at which subjects are fastest at identifying category members, the level at which most of our knowledge is organized, the level that most faithfully mirrors natural kinds, and the highest level at which a single mental image can reflect the entire category.
Basic-level categories tend to rest in the middle of typical general-to-specific categorical hierarchies. For example, in classifying life forms, the basic-level category tends to be at the level of the genus (oak, maple, rabbit, raccoon, etc.) If I run across a tree on a trail, I could call it a "plant", a "tree", a "leaf-bearing tree" a "sugar maple", or a "cutleaf staghorn sumac", but I am most likely to simply call it a "maple". Categories more general than "maple" are likely to be mentally represented as superordinate categories, while categories more specific are likely to be represented as subordinate categories. In studies of the speakers of Tzeltal living in Tenejapa in the Chiapas region of Mexico, anthropologist Brent Berlin and his associates determined that the folk categorization of plants and animals at the basic-level reflected scientific classifications remarkably well, while divergences from basic-level led to significant mismatching.
The modern concept of basic-level categories and its accompanying empirical support was first compiled and articulated by Eleanor Rosch. As it continued to develop, it became known as "the theory of prototypes and basic-level categories", or simply "prototype theory". Prototype theory is widely regarded as a breakthrough in experimental psychology, revolutionizing ideas of categorization and replacing an earlier classical theory which defined categories far more rigidly, in ways that did not match empirical evidence. Rosch's theories were inspired by earlier work by psychologists and anthropologists Robert Brown.
Going hand in hand with the idea of basic-level categories is the idea of prototypicality - that categories have a "radial structure", that is, some category members are more representative of their category than others. For example, a robin is considered a more typical example of a bird than an ostrich is. There is an asymmetrical relationship between prototypical category members and nontypical category members - nontypicals are thought of as possessing similarities with prototypes, while the inverse relationship is far weaker. When given an array of examples, such as a series of colored chips, both adults and children more readily select prototypes as a "typical example" of an arbitrarily defined category, even when the prototype is not a central example of the category as it is defined.
Prototype theory is an important component of modern, empirically verifiable psychological theories. Considering that human cognition is saturated with inferences about categories and category members, both conscious and subconscious, category research is an essential part of uncovering how the human mind works. As psychological research continues to develop and is empowered by increasingly more precise techniques, tools, and theories, categories will be the target of many fruitful research projects.