concept formation

concept formation, process by which a person learns to sort specific experiences into general rules or classes. With regard to action, a person picks up a particular stone or drives a specific car. With regard to thought, however, a person appears to deal with classes. For instance, one knows that stones (in general) sink and automobiles (as a class) are powered by engines. In other words, these things are considered in a general sense beyond any particular stone or automobile. Awareness of such classes can help guide behaviour in new situations. Thus two people in a bakery may never have met before, but, if one can be classified as customer and the other as clerk, they tend to behave appropriately. Similarly, many people are able to drive almost any automobile by knowing how to drive a specific automobile.

The term concept formation describes how a person learns to form classes, whereas the term conceptual thinking refers to an individual’s subjective manipulation of those abstract classes. A concept is a rule that may be applied to decide if a particular object falls into a certain class. The concept “citizen of the United States” refers to such a decision rule, meaning any person who was born in U.S. territory or who is a child of a U.S. citizen or who has been legally naturalized. The rule suggests questions to ask in checking the citizenship of any particular individual. As most concepts do, it rests on other concepts; “U.S. citizen” is defined in terms of the concepts “child” and “territory.” Many scientific or mathematical concepts cannot be understood until the terms by which they are defined have been grasped. In this way concept formation builds on itself.

Conceptual classification may be contrasted with another type of classification behaviour called discrimination learning. In discrimination learning, objects are classified on the basis of directly perceived properties such as physical size or shape. The emphasis on concrete physical features in discrimination learning can be contrasted with the more abstract nature of concept formation. When a stimulus is perceived to match several different past experiences, however, the response may be a compromise, because an object need not bear an all-or-none relation to a set of others in discrimination learning; for example, there is no absolute distinction between tall and short people.

While human beings are capable of abstract thought, many of the classifications people make seem to be concrete discriminations. For example, people may use the same term in a discriminative or conceptual way. A child might use the term policeman in discriminating a man who wears a distinctive uniform, while a lawyer may use the term to represent a civil servant charged with enforcing criminal codes. In practice, people seem to think in ways that combine abstractness and concreteness. They also may blend class membership with assignment along a scale—e.g., such concepts as leadership, an abstract quality that people are said to exhibit in varying degrees. The same would apply to vivacity, avarice, and other personality traits.

People seem to develop more-complex sets of classes than do other animals, but this does not necessarily mean that human modes of learning are unique. It may be that all animals have the same basic biochemical machinery for learning but human animals exhibit it in greater variety. Yet, it seems no more appropriate to account for human concept formation in terms of discrimination learning alone than it does to reduce the functions of a piston engine to chemical reactions.

Experimental studies

Because careful observation of informal, everyday behaviour is difficult, most evidence about human concept formation comes from laboratory subjects. For example, each subject is asked to learn a rule for classifying geometric figures (see table).

The experimenter may concoct the rule that all green objects are called GEK. The subject is shown some of the figures, told which are named GEK, and asked to infer the rule or to apply it to other figures. This is roughly akin to teaching a young child to identify a class of barking animals with the name DOG. In both cases a general rule is derived from specific examples.

The problem of discovering that GEK = GREEN is almost trivial when four GEK and four NOT GEK figures are presented at once, but the problem becomes surprisingly difficult if the figures are presented one at a time and need to be remembered. Furthermore, when two concepts are to be learned together (e.g., JIG = TRIANGLE and GEK = GREEN), memory for each concept tends to be mixed, and it becomes a formidable task to solve either problem. This suggests that short-term memory is important to concept learning and that short-term memory can often serve as a limiting factor in performance. The mastery of more-complex concept learning often depends on allotting enough time for the information to be fixed in memory.

Most such experiments involve very simple rules. They properly concern concept identification (rather than formation) when the learner is asked to recognize rules he already knows. Adult subjects tend to focus on one stimulus attribute after another (e.g., shape or colour) until the answer is found. (This represents problem solving with a minimum of thinking; they simply keep guessing until they are right.) People tend to avoid repeating errors but seem to make surprisingly little use of very recent short-term experience.

Most people try out attributes in an orderly manner, first considering such striking features as size, shape, and colour and only later turning to the more abstract attributes (e.g., number of similar figures, or equilateral versus isosceles triangles). This suggests that there is no sharp distinction between discrimination learning (relatively concrete) and concept formation (more abstract); instead, one progresses from the concrete to the abstract.

Study can shift from concept identification to concept learning by requiring combinations of previously learned rules. A conjunctive concept (in which the rule is based on the joint presence of two or more features; e.g., GEK patterns now are LARGE and GREEN) is fairly easy to learn when the common characteristics stand out. But learning a disjunctive rule (e.g., GEK objects now are either LARGE or GREEN but not both) is quite difficult; there is no invariant, relatively concrete feature on which to rely.

Concept learning in adults may be understood as a two-step process: first the discovery of which attributes are relevant, then the discovery of how they are relevant. In the conjunctive illustration used here, the learner is likely first to notice that size and colour have something to do with the answer and then to determine what it is. This two-step interpretation presupposes that the subject has already learned rules for colour, size, shape, or similar dimensions.

In an example of what is called “intradimensional” shift, initially the subject learns that GEK = GREEN; then, without warning, the experimenter changes the rule to GEK = RED. The same attribute or dimension (colour) is still relevant, but the way in which it is used has been changed. In “extradimensional” shift, the relevant dimension is changed (e.g., from GEK = GREEN to GEK = TRIANGLE), but the classification of some objects does not change (GREEN TRIANGLE is a GEK under both rules). The relative ease with which subjects handle such problems suggests something about how they learn. If they tend to learn simply by associating GEK with specific figures without considering the selected attribute, then they should find extradimensional-shift problems easier, since only some of their associations need be relearned. But if they have learned stepwise in terms of relevant attributes (e.g., to say “What is the colour?…Ah, that colour means it is GEK”), intradimensional shift should be easier, since only the “how” phase of the two-step process need be relearned.

College students tend to find intradimensional-shift problems easier, indicating that they are prone to use the two-step process. On the other hand, suppose a rat initially is rewarded when it runs into the right-hand side of a maze for food, then a change is made by rewarding entries to the left (intradimensional shift) or by rewarding entries to any brightly lighted alley regardless of location (extradimensional shift). The rat will perform best on the extradimensional-shift problem. Among children, performance depends substantially on age. Preschool children are likely to do best with extradimensional shifts (as rats do), but children beyond kindergarten age tend to find the intradimensional shift easiest.

Concepts need not be limited to simple classifications. They also can be interpreted as models or rules that reflect crucial possibilities for change. To take a simple case, an adult is not apt to think that the volume of water changes when it is poured into a container of different shape. Young children may claim that it does. In the adult’s concept, volume is not synonymous with the shape of a container but is based on a model of how fluids behave. Concepts offer a basis for deciding if certain changes will have significant effects.