Categorizing the World: Concepts and Prototypes

To prevent cognitive overload, our brains use concepts—mental groupings of similar objects, events, or people. Without concepts, every new chair you saw would require a brand-new learning process. We organize these concepts into hierarchies to further increase efficiency. These hierarchies typically consist of three levels: the Superordinate (broadest, e.g., 'Animal'), the Basic (most functional, e.g., 'Dog'), and the Subordinate (most specific, e.g., 'Golden Retriever'). Research shows that humans almost always identify objects at the Basic Level first because it provides the most useful information with the least cognitive effort.

Psychologists distinguish between how we define categories. Formal concepts are defined by specific, rigid rules or features. For example, a 'Square' must have four equal sides and four $90^\circ$ angles. If one rule is broken, it is no longer a square. In contrast, natural concepts are 'fuzzy.' They are formed through real-world experience rather than strict definitions. Is a 'Tomato' a fruit or a vegetable? Is 'Video Games' a sport? Because natural concepts lack rigid boundaries, we rely on prototypes—the 'best' or most typical example of a category—to help us decide.

The Prototype Theory suggests that we compare new stimuli to a mental 'average' of that category. The closer an object is to our prototype, the faster we recognize it—a phenomenon known as the Typicality Effect. If your prototype for 'Bird' is a Robin, you will recognize a Sparrow as a bird much faster than you would an Ostrich. Mathematically, we can view the 'distance' from the prototype as $d$. As $d \to 0$, the reaction time $T_{rt}$ decreases. This mental shortcut allows for rapid decision-making but can also lead to stereotyping when applied to groups of people.