Proceedings of the Annual Meeting of the Cognitive Science Society

Theory of mind is a powerful cognitive ability: by the ageof six, people are capable of accurately reasoning about oth-ers’ beliefs and desires. An influential series of language un-derstanding experiments by Keysar and colleagues, however,showed that adults systematically failed to take a speaker’sbeliefs into account, revealing limitations on theory of mind.In this paper we argue that these apparent failures are in factsuccesses. Through a minimal pair of replications comparingscripted vs. unscripted speakers, we show that critical utter-ances used by Keysar and colleagues are uncooperative: theyare less informative than what a speaker would actually pro-duce in that situation. When we allow participants to naturallyinteract, we find that listener expectations are justified and er-rors are reduced. This ironically shows that apparent failuresof theory of mind are in fact attributable to sophisticated ex-pectations about speaker behavior—that is, to theory of mind.