Theory of Mind-the understanding that people have thoughts, wants, and beliefs that influence their interpersonal behavior -is an aspect of social cognition that develops with consistent, increasing complexity across age groups, languages, and cultures. Observed delays in theory of mind development among deaf children and others has led to a conversational account of theory of mind development and its delays in terms of the nature and amount of social communication experienced by children directly (conversationally) and indirectly (via overhearing). The present study explored theory of mind in deaf young adults by evaluating their understanding of sarcasm and advanced false belief (second-order false belief and double bluff), as well as related cognitive abilities. Consistent with previous studies, deaf participants scored significantly below hearing peers on all three theory of mind tasks. Performance was unrelated to their having had early access to social communication via either sign language (from deaf parents) or spoken language (through cochlear implants), suggesting that deaf participants' performance was not solely a function of access to social communication in early childhood. The finding of different predictors of theory of mind performance for deaf and hearing groups is discussed in terms of its language, social, and cognitive foundations.Theory of Mind (ToM), a key facet of social cognition, has been studied by developmental psychologists for decades (for reviews, see Wellman, 2011Wellman, , 2014 and is of broad interest to other disciplines (e.g., cognitive science, philosophy). In their seminal study, Premack and Woodruff (1978) defined ToM as the ability to "impute mental states to self and others" and to cognitively reason about these unobservable states (e.g., belief, knowledge, thinking) to "make predictions about the behavior of self and others" (p. 515). ToM thus involves "meta-representational development" (Baron-Cohen, Leslie, & Frith, 1985) and is "theory-like" in that it makes empirically testable predictions based on metacognitive reasoning about beliefs. As Garfield, Peterson, and Perry (2001) explained: "theory of mind is the cognitive achievement that enables us to report our propositional attitudes [thoughts], to attribute such attitudes to others, and to use such postulated or observed mental states in the prediction and explanation of behavior" (p. 494). Defined in that way, it is clear that acquisition of a ToM is a cognitively complex developmental achievement that is distinct both conceptually and empirically from other, simpler social skills and attributes-like general sociability, intent and desire perception, emotion recognition and empathy-that do not require a meta-representation and are already present in some form by late infancy.ToM typically is assessed using false-belief tasks requiring the prediction of the behavior of protagonists who hold false beliefs that the person being tested does not share. When used with hearing children, false belief tasks normally are spok...