Conceptualizing the Nature of Human Concepts
You see objects moving along a road and mentally represent them in your mind in terms of categories such as “trucks” and “cars.” Trucks and cars are examples of concepts, the mental categories we use to group objects, events, and ideas according to their common features.
A concept is simply a category or class of objects, events, qualities, or relations that share one or more defining features. The defining feature allows us to discriminate the members of one category from the members of another category (or class).
Forming concepts helps us to make sense of the world and prepares us to anticipate or predict future events more successfully. For example, classifying a slithering creature in the woods as a snake prompts us to keep a respectful distance—a response that could be a lifesaver.
Think how differently you’d react to an approaching animal if you classified it a skunk rather than a rabbit. Any species that failed to differentiate between something poisonous and something nutritious, or between a harmless creature and a predator, would quickly become extinct (Ashby & Maddox, 2005).
Imagine, too, what it would be like if you were unable to form concepts. Each time you encountered a four-legged furry creature that went “woof,” you wouldn’t know whether to pet it or to run from it. Nor would you know whether a spherical object placed before you is one to be eaten (a meatball) or played with (a baseball).
Concepts also help us respond more quickly to events by reducing the need for new learning each time we encounter a familiar object or event.
Having acquired the concept ambulance, we immediately know how to respond when we see one pulling up behind us on the road.
Classification of Concepts
It is customary to classify concepts into two major types, logical concepts and natural concepts.
A logical concept is formed by identifying the specific features held by everything that the concept applies to. Thus logical concepts have clearly defined rules for determining membership.
School children, for example, learn that the concept of a triangle applies to any three-sided form or figure. If a figure has three sides, it must be a triangle.
While we do form strictly logical concepts when we need to do so, such as in logical reasoning tasks or in mathematics, in everyday life we usually form “fuzzy concepts” which do not have clearly definable boundaries, of which the rules that determine how they are applied are poorly defined. Such concepts have been termed natural concepts.
Abstract entities such as justice, honor, love, and freedom are classified as natural concepts because people typically use them without applying a strict set of rules to determine how they are to be applied.
Because of the difficulty frequently experienced in defining natural concepts, Eleanor Rosch (1975) proposed that people conceptualize the world in terms of discrete prototypes.
Rosch regarded a prototype as an ideal instance of a concept which thus incorporates the features shared, in different degrees by most instances of the concept. Thus, the concept of a bird allows us to include in it such unbird-like birds as ostriches, penguins, and chickens.
These do not share the most defining feature of birds, which is that they fly, but they do each possess certain features of birds, though not all of the same ones as each other.
According to Rosch, the greater the similarity between an instance and a prototype the more likely we are to consider the instance as a member of a concept which the prototype represents. Thus a robin should be perceived as a more typical bird (i.e., prototype) than a chicken because, while both have feathers and wings, the robin can fly.
Rosch’s ideas about the nature of human concepts revolutionized the experimental study of concept formation. Although there are certain difficulties with her theories which have not been mentioned here, her work and that of her collaborators has contributed to the realization that our thinking is not synonymous with purely logical processing. Her theory has also helped us understand differences in thought processes that are observed between individuals, groups, and cultures.
Hierarchies of Concepts
We typically organize concepts we use within hierarchies that range from broader to narrower categories. For example, one widely used model is based on three-level hierarchy consisting of superordinate concepts, basic-level concepts, and subordinate concepts.
Superordinate concepts are broad categories, such as vehicle, animal, and furniture. Within these categories are narrower basic-level concepts, such as car, dog, and chair, and within these categories are yet narrower subordinate concepts, such as sedan, standard poodle, and rocking chair.
We tend to use basic-level concepts when describing objects, rather than superordinate or subordinate ones (e.g., calling an object a “car” rather than a “vehicle” or a “sedan”) (Rosch et al., 1976). Children also more readily acquire words representing these basic-level concepts than those representing superordinate or subordinate concepts.
You might ask why we humans gravitate toward basic-level concepts?
One reason may be that basic-level concepts provide the most useful information about objects we encounter.
Categorizing an object as a piece of furniture (a superordinate concept) tells us little about its specific features. (Is it something to sit on? To lie on? To eat on?) The features associated with a basic level concept like “chair” gives us more useful information.
Subordinate concepts, like “rocking chair,” are more specific and limited in range. They may be useful in certain situations, but they may also give us more information than we need.
Children learn to narrow and define their concepts through exposure to both positive instances and negative instances of concepts. A positive instance exemplifies the concept, whereas a negative instance is one that doesn’t fit the concept.
A parent of a toddler identifies dogs in the street as “bow-wows,” a positive instance. At first, the child may overextend the concept of “dog” (or bow-wow), calling all animals “bow-wows,” even cats.
But after repeated experience with positive and negative instances of “dogs,” “cats,” and the like, children learn to fine-tune their concepts. They identify features that distinguish different concepts and begin calling dogs dogs and cats cats.
On the other hand, logical concepts are usually acquired by learning formal definitions rather than through direct experience.
We might say to a child each time we see a square figure, “Hey, look at the square here. And, look, there’s another one over there.” But the child will acquire the concept more rapidly by learning the rule that any four-sided figure with sides of equal length is classified as a square.