The robustness of speech-like vocalization in typically developing infants and infants with autism.

Researchers recorded babies' sounds throughout their first year of life. All babies - including those later diagnosed with autism - started making speech-like sounds at the same high rate (about 4-5 per minute). However, boys with autism showed a pattern where their vocalizations decreased over time, while typically developing children and girls with autism maintained steady rates. This suggests early vocal patterns might help identify autism earlier.

This longitudinal study examined speech-like vocalizations ('volubility') in 302 infants across three groups: 127 typically developing, 44 with autism, and 21 with non-autism developmental delay. Through 8.6 all-day recordings per infant across the first year, researchers found that all infants initially produced 4-5 vocalizations per minute. However, important sex differences emerged: boys with autism or developmental delay showed declining volubility over the first year, while typically developing boys and all girls maintained stable rates. The study highlights early vocal development differences that may serve as potential markers for autism identification.

Declining volubility in boys during the first year may serve as an early developmental marker warranting further assessment. Findings support the importance of monitoring vocal development patterns, particularly in male infants, and suggest potential for earlier identification of autism through objective vocal measures.

Study type not specified. Sample sizes for autism (n=44) and developmental delay (n=21) groups were relatively small compared to typically developing group (n=127). Coding methodology limited to 21 five-minute segments per recording may not capture full vocal patterns.

Human infants produce speech-like vocalizations ("volubility") at very high rates, 4-5 per minute during waking hours across the first year, far exceeding rates of our ape relatives. We document volubility in 127 typically developing (TD) infants, 44 with autism (ASD), and 21 with non-autism developmental delay (DD) through longitudinal recordings and human coding. Families of 302 infants (110 not yet diagnosed or with other diagnoses) supplied 8.6 all-day recordings across the first year. Trained coders analyzed 21 randomly-selected 5-minute segments per recording, counting speech-like vocalizations, cries, and laughter.

Infants in all groups (including those with other diagnoses or not yet diagnosed) showed volubility of 4-5 per minute for the first year, but boys showed higher volubility than girls in the TD, ASD, and DD groups. While volubility was relatively stable across the first year for both boy and girl TD infants, volubility fell in both ASD and DD boys, while being more stable for girls. Strong similarities in volubility were seen across all groups, but male infants diagnosed with ASD or DD showed falling volubility across the first year, a pattern not seen in TD infants.