Many aspects of problem solving involve inductive reasoning, or induction. Simply put, induction is a means of reasoning from a part to a whole, from particulars to generals, from the past to the future, or from the observed to the unobserved. Whereas valid deductive inferences guarantee the truth of their conclusions, in the sense that it is impossible for the premises to be true and the conclusion false, good inductive inferences guarantee only that, if the premises are true, the conclusion is probable, or likely to be true. There are several major kinds of inductive reasoning, including causal inference, categorical inference, and analogical inference.

In a causal inference, one reasons to the conclusion that something is, or is likely to be, the cause of something else. For example, from the fact that one hears the sound of piano music, one may infer that someone is (or was) playing a piano. But although this conclusion may be likely, it is not certain, since the sounds could have been produced by an electronic synthesizer. (See also induction, problem of.)

In a categorical inference, one makes a judgment about whether something is, or is likely to be, a member of a certain category. For example, upon seeing an animal one has never seen before, a person with a limited knowledge of dogs may be confident that what he is seeing is a dog but less certain about the specific species.

In reasoning by analogy, one applies what one has learned to another domain. Aristotle stated the formulae for two possible analogical inferences: “As A is to B, so C is to D”; and “As A is in B, so C is in D.” Analogical inference involves applying the outcomes of a known situation to a new or unknown situation. A risk in this approach, however, can occur if the two situations are too dissimilar to merit the analogous comparison.

Judgment

A simple form of realistic thinking—i.e., thinking that is oriented toward the external environment—underlies the ability to discriminate discrete objects or items of information (e.g., distinguishing a lion from a tiger). The outcome is a judgment, and accordingly the process may be called decision making. The availability of information, the rate at which it is presented, the expectations of the person making the judgment, and the number of alternatives available influence the judgment’s accuracy and efficiency. Redundancy (or surplus) of information facilitates judgment. For example, a lion may be identified on the basis of a number of different sensory cues, such as being tan or brown, lacking stripes, having a mane, and so on.

Concept attainment

A more complex form of realistic thinking underlies the ability to identify or use a class of items, as in selecting several different kinds of triangle from an array of other geometric figures. In the course of solving the problem, the individual will link together a newly experienced group of objects according to one or more of their common properties. This new grouping is then given a general name (as in first learning the meaning of the word triangle). It might also be determined that a new object fits an existing category. Physical objects are multidimensional; that is, they may vary in shape, size, colour, location (in relation to other objects), emotional significance, or connotative meaning. How a person identifies such dimensions, develops hypotheses (or tentative conclusions) about which of the specific dimensions define a class, arrives at the rules of class membership, and tests various hypotheses all reflect his ability to grasp concepts. Successful performance in all these processes leads to the formulation of pertinent rules based on one’s ability to classify specific items. (See concept formation.)