Disentangling Language and Education Effects on False Belief Understanding: Evidence From Homesigners, Signers, and Unschooled Spanish Speakers

Disentangling Language and Education Effects on False Belief Understanding: Evidence From Homesigners, Signers, and Unschooled Spanish Speakers Deanna L. Gagne (deanna.gagne@uconn.edu) Department of Psychology, 406 Babbidge Road, Unit 1020 Storrs, CT 06269-1020 USA Marie Coppola (marie.coppola@uconn.edu) Departments of Psychology and Linguistics, 406 Babbidge Road, Unit 1020 Storrs, CT 06269-1020 USA Abstract Howard et al., 2008; Gola, 2012) and complement structures (e.g., deVilliers & Pyers, 2002) have been associated with theory of mind abilities. This is not simply based on linguistic complexity: Hale & Tager-Flusberg (2003) found that training on sentential complements, but not relative clauses, improved children’s ToM performance relative to pre-training levels. Those advocating language- based theories argue that some aspect of language is central to normal ToM development. We cannot easily disentangle these factors in typically developing children because language and social abilities develop simultaneously. By 4-5 years of age, children have amassed enough social experience and language to successfully navigate the gold standard task for assessing ToM: false belief (FB) (e.g., Wimmer & Perner, 1983). Working with deaf individuals who have not acquired conventional language, and instead use gestural systems, called homesign, to communicate (Goldin-Meadow, 2003) enables us to distinguish these factors in ways that other groups cannot. Despite their lack of conventional linguistic input, homesigners who continue to use their gesture systems as a primary language as adults are not socially impaired; they enjoy relatively typical social interactions with their hearing families, friends, and neighbors. While not full languages, mature homesign systems exhibit a range of linguistic properties (e.g., the grammatical relation of subject, Coppola & Newport, 2005). One of the main advantages of research with recently emerging languages is the opportunity to measure the effects of absent or atypical linguistic input, and the linguistic and cognitive benefits conferred by participating in a linguistic community. Neither of the two groups of Deaf participants studied here, Homesigners and Cohort 1 signers of Nicaraguan Sign Language (NSL) (the first group of signers to begin creating the language in the l970s), had access to linguistic input transmitted vertically, that is, from a pre-existing language model. However, Cohort 1 signers did engage in language genesis with their peers (horizontal transmission) (Senghas et al., 2005). NSL signers of all cohorts interact with many other users who use the system as a primary language, i.e., members of the Deaf community in Managua. Though homesigners rely on their gesture systems for their entire lives, the hearing people around them use it only with the homesigner. To investigate the contributions of language and education to Theory of Mind understanding, three Nicaraguan groups were tested using a minimally verbal protocol in which they themselves experienced a false belief instead of being told of one. We also assessed the relationship of executive function abilities to false belief performance. Homesigners, who have no linguistic community, did not succeed on either the False Belief or executive function tasks. Nicaraguan Sign Language users, who have educational experience and are part of an emerging linguistic community, performed the best on executive function, though less well on false belief, than Spanish speakers who have little to no education. This study showed that: without a language community, succeeding on either task is difficult; executive function may not be as tied to false belief performance as previously believed; and education may play a greater role in executive function success than language does. Keywords: Theory of Mind; Simulation Theory; false belief; social cognition; executive function; homesign; Nicaraguan Sign Language; language community; education. Introduction Theory of Mind (ToM), the ability to understand that others have beliefs and desires different from one’s own, and that those beliefs and desires may influence their behavior (Wimmer & Perner, 1983, among others), is a foundational aspect of human social cognition. Whether this ability is primarily driven by language development, life experience, or social interactions is actively debated. Proponents of so-called Simulation Theories argue that life experience and social interactions are sufficient to scaffold mature ToM abilities, without the need for language (e.g., Gordon, 1986; Goldman, 1992). On this view, one’s own experiences provide the foundation for ToM by serving as a template for understanding how others will behave in a given similar situation; these templates are updated as one gains more life experience. Language can play a part, because it provides a way to interact more, and to thus update one’s templates more efficiently, but it is the reflection on one’s own experiences that primarily supports the understanding of other minds. Other researchers argue that language development, and even specific linguistic structures, are essential to the child’s development of a mature ToM. Mental verbs (e.g.,