Canonical Babbling May Differ Between Autistic and Non-Autistic Toddlers in Consonant Transition Probabilities

Canonical babbling is a key stage in speech development, and atypical canonical babbling can be an early sign of speech disability. Speech onset delays and language disability are frequent in autism, but studies that focus on the rate or onset of canonical babbling report mixed findings. Quantity-based metrics can obscure qualitative differences in canonical babbling productions, such as, and more specifically, the sequential organization of syllable transitions, which may be more sensitive to early group differences.

Using at-home recordings of thirty-six 18-month-olds (autistic: n = 10, non-autistic: n = 26), we analyzed transition probabilities of consonant categories (stops, nasals, fricatives, liquids, and glides) within canonical babblings.

In both autistic and non-autistic children, the probability of producing a consonant depends primarily on the immediately preceding one. We did not find any significant difference in the frequency of canonical babbling between autistic and non-autistic children. However, transition structures differed overall (Frobenius distance), and autistic children's sequences were more predictable and less varied (lower Shannon entropy rate), whereas the tendency to repeat the same category (stay probability) did not differ between groups. Finally, several specific consonant transitions were numerically different, but only one (liquid to the end of the utterance) remained reliable after correction and covariate control.

Canonical babbling at 18 months of age reflects local, first-order constraints; in autism, global organization appears more constrained, even though autistic children may babble just as much as their non-autistic peers. Our results provide promising evidence that the structure of babbling, rather than its sheer frequency or segmental diversity, distinguishes the two groups and deserves further exploration.

https://doi.org/10.23641/asha.32513430.