Abstract
The ability to interpret the meaning of metaphorical proverbs has been used not only in intelligence testing but also to investigate abnormalities of thinking in schizophrenia; mainly the theories that schizophrenics are either “concrete” or “overinclusive” in their thinking. The theory of concreteness has been proposed mainly by Goldstein (1946), who held that schizophrenics were unable to adopt the “abstract attitude”, and, having lost the ability to form normal abstract concepts, formed concrete ones instead. Cameron (1946) described overinclusion as one of several abnormalities found in schizophrenic thinking. This abnormality has been adopted by Payne and his co-workers (1957, 1959, 1960, 1962, and 1966) as the basic disorder of schizophrenic thinking. Schizophrenics showing this disorder appear unable to maintain the boundaries of a problem, and so form overbroad concepts. Overinclusion, however, is found in only about 50 per cent. of acute schizophrenics and has also reported in other psychiatric conditions (Payne and Hirst, 1957; Payne and Frielander, 1962; Sturm, 1965).

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