A relatively more recent aggregation of work has further explored the influence of bilingualism on mentalizing or perspective-taking, as well as empathy, on language processing in young children. For instance, at least one recent study found bilingual-speaking youngsters to be more accurate than monolingual speakers in a task that required analyzing an observer’s perspective from different positions
. Moreover, a recent meta-analysis appears to indicate these general findings are robust
. Though it is not fully understood how bilingualism provides this advantage, it has been suggested that bilingualism perhaps allows for additional occasions to develop executive function, metalinguistic comprehension, and improved sensitivity to the nuances of typical sociolinguistic interactions
Over the last few decades, increasing numbers of psychologists and neuroscientists have come to understand that many psychopathologies and developmental disorders can be largely attributed to dysfunctions of the evolved social brain
[50]. In the majority of cases, such dysfunctions typically involve substantive deficiencies in social cognition, social communication, and linguistic abilities. In particular, autism spectrum disorder (ASD) is a heterogeneous disruption of social cognition, generally entailing various social deficits, such as dysfunctions in social communication (e.g., atypical facial expressions and vocal tone), social interactions (e.g., joint attention, eye gaze, and gesture), imitation and social norms, mentalizing, empathy, analogies (e.g., sarcasm and jokes), unfamiliar situations, imagination (e.g., make believe or play), and planning for or predicting future events
[82]. Intriguingly, due to the profound neurogenetic and neurodevelopmental causes, as well as serious dysfunctions in social cognition that define ASD, ASD presents the occasion for neuroscientists, anthropologists, and psychologists to investigate the biological genesis of social cognition and social behaviors inherent to human nature.
8. The Social Brain and Autism Spectrum Disorder
Autism spectrum disorder (ASD) is a neurodevelopmental dysfunction characterized by chronic deficits in social interaction, non-verbal and verbal communication, and social cognition, including deficits in mentalizing or the ability to understand the mental states of another individual
[52][53]. Intriguingly, the complex interrelated genetic, social, and neurodevelopmental pathways and deficits found in ASD, present perhaps one of the clearest and most compelling connections between the social brain, language function, social cognition, and social bonding
[12]. As the name suggests, autism is situated on a spectrum, with some individuals whose verbal capacities exist along the typical spectrum of abilities, while others never learn to speak
[54]. Interestingly, in those with adequate language and cognitive capacities, such as those with Asperger’s syndrome and high-functioning autism (HFA), specifically social communicative capacities ostensibly remain impaired. In other words, communication is typically unidirectional and used instrumentally and non-socially instead of for socially related functions
[55]. Neurological studies on cortical development in language-related areas of the frontal and temporal lobes of the brain have been further correlated with linguistic impairments in ASD, including asymmetrical turnaround of the frontal lobes
[83][64][58], superior and anterior shifting of the left cerebral hemisphere, superior temporal sulcus, and inferior frontal sulcus
[84], bilateral decreases of gray matter volume in the superior temporal sulcus
[85], and apparently overall reduced left hemispheric dominance. Intriguingly, though challenging to disentwine the respective contributions of social cognition deficits in autism to linguistic deficits in autism, several recent studies in both autistic and neurotypical adults and children appear to suggest that mentalizing, which is impaired in autistic individuals, may be integral for the cognitive and linguistic ability to build subordinate and recursive embedded clauses (e.g., ‘‘Mary thinks that Sandra believes the broom is in the closet’’) (see
Figure 2;
[86][63][60]), suggesting another direct link between social cognition and language ability.
Figure 2. Several studies of both autistic and neurotypical adults and children appear to suggest that higher-order mentalizing (i.e., inferring the mental states of more than one individual) may be important for the syntactic ability to build subordinate and recursive embedded clauses (e.g., “Mary thinks that Sandra believes the broom is in the closet”), suggesting a direct link between social cognition and language ability. Adapted image from the public domain.
9. Early Biomarkers of Language-Related Abilities and Relevant Clinical Applications
Describing the early development of neurotypical and neuroatypical language neurobiology is critical for the early identification and potential treatment of clinical language disorders. Crucially, delays in language and speech in infants and children can negatively affect important social and academic skills such as attention, reading, writing, social interactions, and, of course, later educational outcomes
[61]. For instance, delays in language acquisition from 2–5 years are implicated in substandard reading comprehension in the classroom
[62][65]. If such language delays persist after 5 years, related challenges often persist in the consequent maturation of attention, directed eye gaze, and socialization
[61][66]. The majority of language delays are often noticed during parental observations or clinical check-ups when an important developmental landmark does not appear to be present, like syntactic challenges or speech onset delays. As a consequence of this rather crude ‘sit-and-wait’ approach, most youngsters are unfortunately not characterized as having had a disorder or delay of language until 2–3 years of age, which is often noted by the absence of combinatorial speech, or the capacity to formulate words into complete thoughts and sentences
[61][87].
An alternative approach emphasizes the emergence of early indications, or biomarkers, of ultimate language capacities, early enough in development, to establish that any clinical interventions into speech and language delays and disorders might provide the greatest benefits. Perhaps surprisingly, there are currently no standardized or universally agreed-upon criteria in screening for language and speech deficiencies.
As might be expected, the diagnosis of language delays and disorders is usually grounded in comparable maturational landmarks observed in neurotypical language learning [88]. Children with language delays typically adhere to a normal maturational trajectory, albeit at more sluggish rates than would be expected [89], whereas children with language disorders tend to display regressions in language development (e.g., word loss from 14–21 months of age in ASD), serious and persistent delays in language learning (e.g., challenges with syntax in youngsters with specific language impairment (SLI), or impairments in at least two domains of development (e.g., such as motor function and language impairments in global developmental delay (GDD) [88][90][91]. As a general rule-of-thumb, language delays typically require clinical intervention when the development rate drops beneath 3/4 of the rate expected, for example, when a standard developmental landmark typically observed at 2 years of age fails to be met in a youngster at 30 months of age [92].
Nonetheless, speech and linguistic interventions should arguably begin even earlier in development. In fact, speech processing already begins in utero, in spite of the fact that the more observable first 24 months are distinguished by more obvious mappings of form-to-meaning at 5–7 months of age and proficiency at distinguishing native sounds from 6–12 months of age [93].