This paper investigates what makes something funny. Incongruity (that is perceiving a situation from different viewpoints and finding the resulting interpretations to be incompatible) seems to contribute to sensations of mirth. In this paper, a computational model of sentence comprehension is used to formalize incongruity and test its relationship to humor in puns. By combining a noisy channel model of language comprehension and standard information theoretic measures, the researchers identify two dimensions of incongruity-ambiguity of meaning and distinctiveness of viewpoints-and use them to predict humans' judgments of funniness. Results show that both ambiguity and distinctiveness are significant predictors of humor.