Cooing, the production of open, vowel-like sounds like “ooh” and “aah,” is one of the earliest forms of communication an infant develops. These sounds typically emerge around two months of age and are often expressions of contentment or happiness. Cooing is followed by babbling, which incorporates consonant sounds to form repeated syllables such as “ba-ba” or “ma-ma,” and is a fundamental step toward spoken language.
Typical Development of Infant Vocalizations
Infant vocal development begins with reflexive sounds, such as crying, sneezing, or burping, which are present from birth. Around two to four months, the infant progresses to cooing, characterized by long, drawn-out vowel sounds. This stage is when the infant starts to explore the vocal tract.
By four to six months, cooing transitions into vocal play, which includes giggling, squeals, and “raspberries,” alongside the introduction of early babbling. Canonical babbling, a major milestone, typically appears between six and nine months, involving the reduplication of consonant-vowel combinations like “dadada.” This is followed by variegated babbling, where the consonant and vowel sounds change within a string, sounding more like conversational speech without actual words.
These milestones are general timelines, and individual variation in the timing of their appearance is normal. A lack of any vocal sounds by six months or a failure to make both consonant and vowel sounds by seven months are points for discussion with a healthcare provider.
Vocalization Differences Observed in ASD
The question of whether infants later diagnosed with Autism Spectrum Disorder (ASD) coo and babble is not a simple yes or no, but rather a matter of quality and frequency. Many infants who later receive an ASD diagnosis do produce cooing sounds, but differences often become more noticeable as they move into the babbling stage. Research suggests that infants later diagnosed with ASD may show a reduced overall rate of vocalizations, or “volubility,” particularly beginning around 12 months of age.
The complexity and variety of sounds produced can also be affected, with a tendency toward less complex vocalizations compared to typically developing peers. Specifically, infants later diagnosed with ASD are less likely to be in the canonical babbling stage and may demonstrate significantly reduced canonical babbling ratios. While some studies find no difference in the sheer number of vocalizations at six months, a divergence in trajectory often appears during the second half of the first year.
Beyond Cooing: Other Early Communication Red Flags
While differences in vocalizations can be an early indicator, non-vocal and social communication challenges are often stronger red flags for ASD in infancy. One of the earliest signs is a lack of or inconsistent eye contact, which typically begins to develop in the first few months of life. Infants with developing ASD may also show a failure to respond to their name when called, a skill most typically developing infants achieve by 12 months.
Another significant difference is in the use of gestures, particularly pointing, which is a foundational skill for joint attention. Joint attention is the shared focus between an infant, another person, and an object.
Reduced social reciprocity, meaning a lack of back-and-forth social interaction like reciprocal smiling or engaging in games such as peek-a-boo, is also a common observation.
Next Steps: Consulting a Specialist
Noticing any of these differences in vocal or social development does not automatically lead to an ASD diagnosis, but it does warrant a conversation with a healthcare provider. The American Academy of Pediatrics recommends developmental screenings at specific well-child visits, and parents can proactively request one if they have concerns.
The pediatrician may recommend a formal screening tool, such as the Modified Checklist for Autism in Toddlers, Revised (M-CHAT-R), and potentially refer the child to specialists. These specialists might include a developmental pediatrician, a child psychologist, or a speech-language pathologist for a more comprehensive evaluation.
Seeking early detection is a proactive step that allows for timely intervention, which can significantly improve long-term outcomes, regardless of the final diagnosis.