Understanding metaphorical comparisons: Beyond similarity.

Traditionally, metaphors such as job is a jail have been treated as implicit similes (i.e., this metaphor would be treated as if it were a comparison statement, job is like a jail). Tversky's account of similarity is applied to such nonliteral similarity expressions, and is shown to apply as readily to nonliteral comparisons as to literal comparisons. But treating metaphors as comparison statements fails to account for certain important phenomena, including metaphoricity itself (the judgment that a comparison statement is nonliteral). We argue that metaphors are exactly what they appear to be: class-inclusion assertions, in which the topic of the metaphor (e.g., job) is assigned to a diagnostic category (e.g., entities that confine one against one's will, are unpleasant, are difficult to escape from). In such assertions, the metaphor vehicle (e.g., jail) refers to that category, and at the same time is a prototypical exemplar of that category. This account of metaphor provides a basis for a theory of metaphor comprehension, and also clarifies why people use metaphors instead of similes. How do people understand nonliteral expressions such as my grandfather is a baby? Taken literally, this sentence seems false. A grandfather must be an adult, and an adult cannot be of an age to be included in the category baby. According to traditional theories of metaphor comprehension (see Ortony, 1979a), the listener must reject this false literal interpretation and somehow find a nonliteral interpretation that is appropriate to the context of the conversation. In terms of speech act theory, where an utterance is defective if taken literally, look for an utterance that differs from sentence meaning (Searle, 1979, p. 114, italics added). A comprehension model based on this assumption postulates three stages: