Updated: Apr 10, 2020
Kuhl’s review paper links the social brain and language development in infants through past findings to develop a novel model of early speech learning. The hypothesis that social interaction is essential to language development. The model, derived from the examination of Kuhl’s research, allows us to zoom in on the language aspect of autism. Thus, her research may suggest ways speech therapy and enhanced social interaction may deter the effects of differential speech acquirement in individuals with autism.
This paper looks at autism through a linguistics window. The social brain, which rapidly develops in the first months of life, is the “gate”-keeper of speech learning. Native-language phonetic perception changes between 6-12 months in which babies begin to categorize phonetic units in their language. This is accomplished through social cues and semantics that reinforce language-acquirement by the caregiver or teacher of the child. Khul analyzes past studies to introduce her Native Language Magnet-Expanded (NLM-e) model of phonetic learning. This model describes neural integration of language in two ways: infants must be attracted to infant-directed (ID) speech and social signals enhance learning since they provide enriched information.
This paper gives a thorough history of linguistic studies that reinforce the idea social interaction is essential for normal language requirements; the focus and timeline of development are clear and elaborated on. Kuhl points out that a critical time for language expression is 6-12 months. This is consistent with broader studies of neonatal transitions in that distinct vocalizations begin for 95% of babies at six months (Shultz, et. al., 2018). The analogy of social interactions as a “gate” to speech learning allows the reader to see this finding as a pivotal moment in developmental linguistic studies related to autism. The mechanism that allows infants to mimic sounds that are human-like and not, let's say, chimp-like is due to the reinforcement that caregiver interactions provide (Kuhl, 1991). I believe the term “gate” is an excellent way to consolidate the vast findings discussed in the paper. Another strength of this study was Figure 2 which incorporates previous studies as well as the phases of the NLM-e model. It creates a great reference that summarizes the paper.
An aspect that was confusing about this paper was whether the NLM-e model applies to children with high-functioning autism after the first years of life. A study found that after three years of age, there was no difference in verbal and nonverbal scores of normal and high-functioning children with autism (Paul, 2008). Kuhl generalizes that “children with ASD do not prefer ID speech,” which, if true, does not have an impact on explicit language skills of those with verbal, high-functioning autism. Additionally, Kuhl compares language deficits in babies who grew up in social isolation as equivalent to those who have autism. Although there is merit in this argument, her correlation was not clear.
Kuhl and her colleagues compiled convincing evidence that live interactions in a foreign language with 9-month-olds had lasting effects on recognizing the foreign phonetics even after a significant break from exposure (Kuhl et. al., 2003). A worthy longitudinal study would see if those children had an easier time learning that language in teenage or even adult years. If there is a positive correlation between learning and early exposure, these results would reinforce the idea that plasticity and adaptions of the neuronal circuits created in early development are long-lasting.
Kuhl, P.K., Tsao, F.-M., & Liu, H.-M. (2003). Foreign-language experience in infancy: effects of
short-term exposure and social interaction on phonetic learning. Proceedings of the National Academy of Sciences, USA, 100, 9096–9101.
Kuhl, P.K., Williams, K.A., & Meltzoff, A.N. (1991). Cross-modal speech perception in adults and infants using nonspeech auditory stimuli. Journal of Experimental Psychology: Human Perception and Performance, 17, 829–840.
Paul, R. , Chawarska, K. , Cicchetti, D. and Volkmar, F. (2008), “Language outcomes of toddlers with autism spectrum disorders: a two year follow‐up” Autism Res, Vol. 1: 97-107. doi:10.1002/aur.12
Shultz, S., Klin, A., Jones, W. (2018) Neonatal transitions and their implications for autism. Cell Press Reviews, vol. 22, pp. 452-469 doi: https://doi.org/10.1016/j.tics.2018.02.012