Concept

Concepts: What Makes a Bird a Bird?

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.

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 as 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 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.

Types of Concepts

We can classify concepts into two major types, logical concepts and natural concepts.

1. Logical concepts

Logical concepts have clearly defined rules for determining membership. Schoolchildren, 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.

2. Natural concepts

Most concepts we use in everyday life are natural concepts, in which the rules for determining how they are applied are poorly defined or fuzzy.

Abstract concepts such as justice, honor, 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.

Objects such as mammals and fruits may be used as either logical or natural concepts. For example, most people use a natural concept of “fruit” because they lack a precise idea about what makes a fruit a “fruit.” They might readily agree that an apple is a fruit, but be unsure whether an avocado, a pumpkin, or an olive is a fruit.

A botanist, however, is likely to use fruit as a logical concept by applying it only to objects that meet a specified botanical criterion (e.g., the ripened reproductive parts of seed plants). But what makes a fruit a fruit in the way most people typically use the concept? Typically, people base their judgment on taste (fruits are typically sweet, whereas vegetables are generally savory) rather than a botanical criterion.

How do we determine whether a particular animal—say, an ostrich or a penguin—is a bird? One commonly used basis for categorization involves judgments of probability—judging the likelihood that a particular object belongs to a particular category (Willingham, 2007).

Figure X | Is a penguin a bird? Although a penguin doesn’t fly, it is classified as a bird. Yet people may not recognize it as a bird if it does not closely resemble the mode of a bird they have in mind, such as a robin. Image courtesy of Calgaryzoo Opens in new window.

In forming these judgments, people perform a mental operation of comparing an object’s characteristics with those of a model or example of a category member to determine whether the object is a good fit to the category.

For example, they might think of a robin as a model or “best example” of a bird. They then classify a sparrow as a bird more readily than they would an ostrich or a penguin because the sparrow has more robin-like feature (sparrows fly; ostriches and penguins don’t).

Hierarchies of Concepts

We typically organize concepts we use within hierarchies that range from broader to narrow categories. For example, one widely used model is based on a three-level hierarchy consisting of superordinate concepts, basic-level concepts, and subordinate concepts (Rosch et al., 1976).

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 superodinate 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.

Why do people gravitate toward basic-level concepts?

One reason may be that basic-level concepts provide the most useful information about objects we encounter. Categorizing Opens in new window 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” give 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 refine 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.