A procedure for testing the ability to use concepts. A subject is presented with three or more items to see if he can pick out the odd one, the one that does not belong with the rest.The oddity method can be applied with or without the use of language. In a typical verbal test, the subject is asked, Which of the following does not belong with the other: skyscraper, temple, cathedral, prayer? In a performance test, the subject looks at a group of actual items or pictures and picks out the odd one. This form of the test can be applied to young children and even certain animals. In one setup three hollow geometrical forms are presented, with a reward such as candy or fruit placed under the odd-shaped one. After the subject solves this problem,he is presented with other sets of three to see if he continues to choose the odd shape. This would indicate whether he could detect a relationship, and, presumably, form a concept.The oddity method is used in experimental work (Cofer, 1951) as well as intelligence tests. It offers an alternative to the usual ways of determining whether a subject can understand concepts—that is, by defining terms, giving illustrations, or picking out examples from a group of items (for instance, pointing to vegetables in a group of foods). The verbal oddity test shows whether the subject can understand several concepts at once. It also indicates whether he can form his own concept, or hypothesis, and use it in finding the odd item. Experiments indicate that people can often solve oddity problems even when they cannot give adequate definitions. They have learned their concepts through experience, and they have a practical rather than theoretical understanding of them.Interestingly, it has been found that the order of presentation often determines the basic concept that is used in searching for the odd item. In the example given above, the word “prayer” is usually selected as the one that does not belong. But if prayer is given first, the subject thinks in terms of religious rather than architectural concepts, and usually selects “skyscraper” as the odd item. This ties up with other observations which show the importance of “primacy”—that is, the beginning of a speech or article generally has the greatest effect.Experiments with performance items indicate that chimpanzees as well as children are capable of solving some of the oddity problems (PLATES 36 AND 37). In other words, concept formation is possible even without the use of language.