Nicaraguan Sign Language and Theory of Mind: the issue of critical periods and abilities

Abstract

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.

Editorial: The neuroscience of theory of mind

“…Moreover, even after accounting for the child's own language skills, the child's performance on the false belief task is independently predicted by the mother's proficiency with sign language, and specifically her use of mental EDITORIAL iii state words (Moeller & Schick, 2006). A recent investigation of Nicaraguan Sign Language suggests that performance on non-verbal false belief tasks is predicted by the age at which the child first learned sign language, and not by the number of years that they have been using it (Morgan & Kegl, 2006); children who first entered the sign language community before age 8 perform significantly better than those who did so later in life. Deaf children of native signers *who learn sign language from birth *show no delay at all (de Villiers, 2005).…”

Mental state language and quality of conversational experience in deaf and hearing children

“…In the early stages of social cognitive development these children, even with early cochlear implants might experience a different quality of conversation and interaction during the period their parents adapt to their infant's deafness. Many previous studies have reported that deaf children aged 4 years and above and from hearing families who do not use sign language effectively, display a protracted delay in Conversational input to deaf children 4 Theory of Mind (ToM) reasoning on explicit tests (Courtin & Melot, 2005;Figueras-Costa & Harris, 2001;Meristo, Hjelmquist, Surian & Siegal, in press;Morgan & Kegl, 2006;Pyers & Senghas, 2009;Peterson & Siegal, 1995, 1999Schick, de Villiers, de Villiers, & Hoffmeister, 2007;Woolfe, Want, & Siegal, 2002). In elicited response methodologies the child is explicitly required to respond overtly to a question or prompt about the mental states of another person in the test.…”

The Socio-religious Brain: A Developmental Model

“…Just as children acquire language and theory of mind (ToM) according to distinct but typical developmental patterns, they also acquire the significant features of their own cultures (beliefs, behaviours, rituals, etc.) in a predictable progression of maturation (Morgan & Kegl 2006). The process of enculturation could potentially have innate features -perhaps we also have a 'universal grammar' for religion as we do for language (Alcorta 2006;Bloom 2007;Bulbulia 2005).…”