Evaluating canonical babbling ratios extracted from day-long audio recordings in infants later diagnosed with autism spectrum disorder.

Canonical babbling (CB) is a critical developmental milestone that typically occurs in the second half of the first year of life. Studies focusing on CB in infants at elevated familial likelihood for autism spectrum disorder (ASD) or who later receive an ASD diagnosis are limited and the evidence is mixed. CB comprises a series of canonical syllables (CS) which are defined as the rapid transitions between consonant-like sounds paired with vowel-like sounds (e.g., [gugugu]). One way of measuring CB is by computing canonical babbling ratio (CBR) i.e. total number of CS divided by the total number of syllables. If the child has reached the criterion of 0.15 CBR it is said that they have achieved the CB stage. For several years now, CB has been measured using short lab based or home-based video recordings which may not represent a child's natural vocalization pattern since child vocalizations fluctuate throughout the day. Day long audio recordings, that capture a child's vocalizations throughout the day, has the potential to overcome this limitation. Therefore, the current study aimed to answer whether CBRs computed from day-long audio recordings using the language environment analysis (LENA®) were different among infants at elevated familial likelihood for ASD who receive an ASD diagnosis (EL-ASD; n = 11), who did not receive an ASD diagnosis (EL-Neg; n = 32) and infants at low likelihood for ASD (LL-Neg; n = 25) at 9 and 15 months. The study also aimed to evaluate if there are group differences in reaching the canonical babbling stage at 9 and 15 months and are CBRs at 9 and 15 months associated with later language abilities at 24 months. Findings indicated no group differences in mean CBRs at 9 and 15 months and no association with later language abilities. However, we found that children in the EL-ASD group were less likely to reach the 0.15 CBR threshold for being in the canonical babbling stage by 9 months of age. Thus, suggesting that a diagnosis of ASD is associated with delays in CB for some children. Future work in this area must include a larger sample and more standardized annotation protocols to harmonize results across studies and ensure replication.