Do Non-Verbal Autistic Children Process and Understand Spoken Words Differently?

Non-verbal autistic children may experience significant delays in speech processing, leading to deficits in communication as compared to both neurotypical children and other autistic but verbal ones. 

Communication is one of the biggest difficulties faced by autistic children, as many struggle with responding at a level that neurotypical children would be expected to — often lacking in depth or relevance, and appropriate tone or volume (Vogindroukas et al., 2022). In fact, the ability to use verbal language as a form of communication is a determining factor in classifying types of autism officially by the International Classification of Diseases (ICD-11) (International Classification of Diseases, 2021). However, while deficiencies in conversational responses provided by autistic children can be observed rather easily, what is less obvious is their processing and understanding of the spoken information they receive. Additionally, children with low or no verbal means for communication (also known as non-verbal), may experience spoken words differently as they themselves do not use it to communicate. 

On a physical level, the brains of autistic children differ from neurotypical ones, including the areas which are responsible for processing and producing speech. Studies on speech processing within autistic individuals found that almost every step of analysing speech differs between neurotypical and neurodivergent people, from identifying speech sounds to understanding what the spoken words mean (Key & Slaboch, 2021). 

For neurodivergent children, it has been suggested that the reason why they may lack the speech processing capabilities of their neurotypical peers is due to the brain allocating fewer resources towards the intake and subsequent comprehension of verbal information (Key & Slaboch, 2021). Multiple studies have also found there to be less grey matter in speech and language specific areas of the brains of autistic children (Frances et al., 1999), as well as abnormal shapes and sizes of these brain areas — a difference which is further amplified for the autistic children who have language impairments (Dé Fosse et al., 2004). 

Psychological reasons may also affect autistic children’s speech comprehension and processing abilities. A lack of inherent interest or motivation to engage in communication, for example, may greatly hinder the amount of attention given to speech processing and production (Key & Slaboch, 2021; Su et al., 2022). 

An inability or unwillingness to produce oral speech sounds is a relatively common occurrence in children with autism, referred to most as being non-verbal. Due to the presentation of autism being unique to each person, theories on the causes for non-verbal autism are varied. Generally, it is agreed that to some degree it is the cognitive mechanisms and brain structure affecting whether an autistic person would have spoken language developmental delays or be unable to communicate verbally (Posar & Visconti, 2021). There are also suggestions that genetics or environmental factors may contribute to a child’s likelihood of being nonverbal, but there is not yet enough research proving the significance of these. 

For non-verbal children, research indicates that compared to their autistic peers of similar intellectual abilities who were verbal, they were less able to properly distinguish differences and changes in speech sounds (Matsuzaki et al., 2019). This is compounded onto the general deficiencies in communication and speech processing that verbal autistic children experience as compared to neurotypical children. This difficulty may be due to the autistic children actively stopping responses to speech, as a result of deficits in the way their brain treats incoming speech sounds (Whitehouse & Bishop, 2008). 

Hence, it can be concluded that in general, non-verbal autistic children face greater difficulties in trying to understand spoken words typically. It is not so much a difference in understanding speech words, but rather a significant delay in it. However, research has also suggested that while the discrepancies in speech processing and language delays are most pronounced in childhood, the brains of non- or minimally-verbal children have a possibility of “tuning” themselves to become more adapted to processing spoken words efficiently (Matsuzaki et al., 2019; Picton et al., 2007). This may explain why some non-verbal children eventually develop language skills that are similar to previously verbal autistic peers. However, as always, it depends greatly on each child, as autism presents itself differently in each one. 

Even if a child remains non-verbal, their speech processing ability could have shown significant improvements. Parents should still communicate with their child frequently both with spoken and non-speaking methods that the child is comfortable with as doing so could encourage development of brain matter in language areas and neural pruning — emphasising on spoken language and speech discrimination as “important” to retain — and potentially help the child process speech more effectively (Matsuzaki et al., 2019).

Written by Kai 

References

De Fossé, L., Hodge, S. M., Makris, N., Kennedy, D. N., Caviness, V. S., McGrath, L., Steele, S., Ziegler, D.A., Herbert, M. R., Frazier, J. A., Tager‐Flusberg, H., & Harris, G. J. (2004). Language‐association cortex asymmetry in autism and specific language impairment. Annals of Neurology, 56(6), 757–766. https://doi.org/10.1002/ana.20275

International Classification of Diseases, Eleventh Revision (ICD-11), World Health Organization (WHO) 2019/2021 https://icd.who.int/browse11. 

Key, A. P., & Slaboch, K. D. (2021). Speech Processing in Autism Spectrum Disorder: An Integrative Review of Auditory Neurophysiology Findings. Journal of Speech Language and Hearing Research, 64(11), 4192–4212. https://doi.org/10.1044/2021_jslhr-20-00738

Lach, R. (2021). Two teenage girls laying on grass and playing telephone call using paper cups on string. Pexels. https://www.pexels.com/photo/two-teenage-girls-laying-on-grass-and-playing-telephone-call-using-paper-cups-on-string-10601908/ 

Matsuzaki, J., Kuschner, E. S., Blaskey, L., Bloy, L., Kim, M., Ku, M., Edgar, J. C., Embick, D., & Roberts, T. P. L. (2019). Abnormal auditory mismatch fields are associated with communication impairment in both verbal and minimally verbal/nonverbal children who have autism spectrum disorder. Autism Research, 12(8), 1225–1235. https://doi.org/10.1002/aur.2136

Posar, A., & Visconti, P. (2021). Update about “minimally verbal” children with autism spectrum disorder. Revista Paulista De Pediatria, 40. https://doi.org/10.1590/1984-0462/2022/40/2020158

Su, P. L., Rogers, S. J., Estes, A., & Yoder, P. (2020). The role of early social motivation in explaining variability in functional language in toddlers with autism spectrum disorder. Autism, 25(1), 244–257. https://doi.org/10.1177/1362361320953260

Vogindroukas, I., Stankova, M., Chelas, E., & Proedrou, A. (2022). Language and speech characteristics in autism. Neuropsychiatric Disease and Treatment, Volume 18, 2367–2377. https://doi.org/10.2147/ndt.s331987 

Whitehouse, A. J., & Bishop, D. V. (2008). Do children with autism ‘switch off’ to speech sounds? An investigation using event‐related potentials. Developmental Science, 11(4), 516–524. https://doi.org/10.1111/j.1467-7687.2008.00697.x