Use of Communicative Gestures in School-Age Children and Adolescents with Nonverbal Autism

Background: Language is estimated not to develop in at least 25% of individuals on the autism spectrum, forming its most severe and understudied end. More studies of nonverbal cognition and communication in this population are urgently needed. A specific research desideratum is to profile nonverbal communicative gestures, some subtypes of which have been shown to be closely linked to language development in both typical and atypical populations.

Objectives: We aimed to shed light on language-gesture relationships by profiling production rates and types of nonverbal communicative gestures in this nonverbal population. Furthermore, we explored the interaction of gestural profiles with different measures of nonverbal cognition and receptive language.

Methods: 19 subjects were recruited from special schools in the Barcelona area. The examiner-child interaction during the ADOS was analysed and coded for gesture use. Standardized measures of nonverbal IQ (as measured by Leiter-R) and nonverbal symbolic cognition (as measured by the ComFor) were also taken. Language status as a recruitment criterion was confirmed in production and comprehension assessed through diagnostic interviews (ADOS and ADI-R), teacher informants, and standardized language tests (Peabody Picture Vocabulary Test-III, and CELF-5 where possible).

Results: All subjects proved to be testable and had comprehension scores commensurate to production ones. Overall rate of production of communicative gestures was low as well, although in a study run in parallel, mean-rank distributions of gesture rates in typically developing pre-verbal infants between 9 and 22 months were interestingly not significantly different. Qualitative gesture profiling however showed the complete absence of declarative gestures including distal pointing. Even distal imperative pointing was scarce at group level, as were iconic gestures, which were produced with an imperative purpose in a strictly embodied context. The proportion of bimodal communicative acts (gesture + vocalization) was significantly lower than gesture-only acts. 79% of individuals scored ≤70 in nonverbal IQ. The remaining 21% of individuals above the cut-off for intellectual disability (ID) did not show different tendencies in any of the measures taken in comparison with the rest of the sample with ID. Neither language nor gesture scores correlated with levels of nonverbal symbolic cognition, which in turn were significantly correlated with nonverbal IQ.

Conclusions: This study provides evidence that in a population of both productively and receptively non-verbal school-age children and adolescents, nonverbal gestural communication changes fundamentally along with language, though this change is not seen quantitatively in communication rates. In particular, gesture types relating to certain restricted forms of referentiality were not present in this group, which would be predicted from independent evidence of their language-relatedness. Moreover, the same linguistic and gestural profile is seen in both high and low nonverbal IQ scores. These results inform debate on how verbal so-called ‘nonverbal’ communication is, and the debate on the role of language in autism at large.