Evolutionary Linguistic Theory - Current Issue

Has language developed to serve as a system of communication or one of thought? While language is clearly an excellent tool for communication, the possible contribution of higher order cognitive processes other than language to communication may provide insights on how we think about language evolution. Studies show that bilingualism improves communication skills, possibly due to boosting domain general processes, thus suggesting a divide between communication and formal language. However, to date little attention has been paid to bilingual atypical child populations presenting asymmetric developmental delays in language and communication skills. In this study, we explore the language-communication divide in bilingual and monolingual children diagnosed with High Functioning Autism (HFA), displaying primary communication difficulties, and those with Specific Language Impairment (SLI), displaying primary language difficulties. Children were tested on language, cognitive control, Theory of Mind (ToM), social comprehension and verbal communication. Results demonstrate that bilingual children with HFA exhibit enhanced cognitive control, ToM and social comprehension, which in turn improve their verbal communication as compared to their monolingual peers with HFA. On the other hand, no boost emerges in bilingual children with SLI, be it in cognitive control or ToM, though a weaker advantage (relative to the children with ASD) can be observed in their verbal communication skills, with significant mediation from social comprehension. The overall evidence suggests that language, though useful for communication, is not sufficient for communication, and may arguably not have evolved primarily for communicative purposes.

In this review, we summarize studies investigating comprehension of three core grammatical structures (Subject-Verb-Object word order, grammatical aspect and wh-questions) in diverse samples of Mandarin-acquiring preschoolers with ASD, all utilizing the Intermodal Preferential Looking (IPL) paradigm. Results showed that children with ASD, though they were delayed in chronological age and expressive language (including significantly lower vocabulary production scores), acquired various grammatical constructions similarly to their typically developing peers. Moreover, Mandarin-acquiring preschoolers with ASD demonstrated similar acquisition patterns of these three core grammatical structures, as has been reported in previous IPL studies among English-acquiring children with ASD (Naigles & Fein, 2017). Thus, the results testify that universal underlying mechanisms are playing vital roles in grammatical acquisition of children with ASD across languages (e.g., the setting of word order parameters, the preservation of functional morphemes, the universal operation of WH-Movement), despite their pervasive social cognition impairments. These findings suggest that core grammatical knowledge may be preserved in children with ASD, even in the face of radical differences in language environment and social/communicative deficits, supporting the contribution of the language faculty in autistic language acquisition. The results shed light on the sharp contrast between linguistic competence (governed by the internal computational system of the language faculty) vs. linguistic performance (affected by loci of impairment in the sensory-motor and the conceptual-intentional interfaces) in ASD. Furthermore, the results highlight the dissociation between the lexical vs. the grammatical modules in ASD, supporting a modular view of the diverse language domains in the language faculty.

Previous research has demonstrated that speakers adapt individual characteristics of speech production to the social context, for example via phonetic convergence. Studies have measured the impact of social dynamics on convergence in typical speakers, but the impact of individual differences is less well-explored. The present study measures phonetic convergence before and after a cooperative interaction with an undergraduate student by comparing teens with a history of autism spectrum disorder (ASD) and with typical development. Results revealed a small temporal convergence effect for typically developing dyads; in contrast, dyads including autistic teens showed no convergence. Furthermore, the degree of convergence was negatively related to severity of ASD symptomatology and atypical sensory profiles. While social and sensory processing abilities may play a role in phonetic convergence, high covariance between these measures makes it difficult to differentiate their contributions in isolation.

Linguists have long sought to draw support from developmental disorders like Williams Syndrome (WS) and Specific Language Impairment (SLI) for linguistic theories and the modularity of language in particular. Linguistic diversity in the autism spectrum (ASD) has received comparatively little attention from linguists. Here I argue, against recent claims to the contrary, that language patterns in ASD do not support the modularity of language any more than WS or SLI are by now acknowledged to do. Rather, conceptualizing the linguistic diversity in question requires integrated neurocognitive models in which language is an inherent aspect of human-specific forms of cognition, social interaction, and communication. ASD can be seen as providing us with important indications of how these are linked.