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Background:  Previous studies in the literature report that deaf individuals who experience late access to language perform poorly on false belief tests of Theory of Mind (ToM) compared with age‐matched deaf and hearing controls exposed to language early. Methods:  A group of 22 deaf Nicaraguans (aged 7 to 39 years) who learned Nicaraguan Sign Language (ISN) at different ages were tested on a false belief and a nonverbal cartoon retell task designed to elicit talk about the contents of character's mental states. Results:  Access to sign language by 10 years of age with possible advantages in language fluency was a strong predictor of performance on both the false belief task and mental state narrative task. However, a comparison of performance on the two tests indicated that children and adults who learned sign after the age of 10 were still able to demonstrate a more general ability to use mental state expressions in narratives. Results are discussed in terms of late access to language and critical periods for the parallel development of Theory of Mind and language. Conclusions:  The findings point to age 10 years as a crucial period when lack of language exposure can lead to long‐lasting deficits in false belief abilities. Late exposure to sign language does not, however, rule out all aspects of the ability to consider others’ mental states. This paper also highlights the need to take into consideration a variety of communication responses when evaluating deaf children's ToM reasoning.

The distribution of null arguments across languages has been accounted for in terms of two distinct strategies: licensing by agreement and licensing by topic. Lillo-Martin (1986 claims that American Sign Language (ASL) exploits both strategies for licensing null arguments, depending on the morphological characteristics of the verb. Here we show that this is incorrect. Once the nonmanual correlates of agreement features (comparable to the nonmanual expressions of other syntactic features) in ASL are recognized, it becomes apparent that null arguments in this language are systematically licensed by an expression of syntactic agreement.

Grammatical information in ASL can systematically be marked on the face. Such nonmanual marking extends over the c-command domain of the trigger, and therefore provides information about the hierarchical organization of the language. Consistent with evidence available from the distribution of non-manual markings—as illustrated with respect to wh-marking and negation—a basic clausal structure for ASL is proposed. Furthermore, we suggest, contrary to generally accepted claims about ASL, that both Tense and Agreement are structurally present in all ASL main clauses. This analysis allows for a uniform account of the licensing of null subjects in ASL. Evidence in favor of this analysis, and against a dual licensing mechanism (as proposed in Kegl, 1985, and Lillo-Martin, 1986, 1991b), is presented.

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