Vocalisation Repertoire at the End of the First Year of Life: An Exploratory Comparison of Rett Syndrome and Typical Development.
Track the CBRUTTER ratio; a score ≤0.15 at 9 months is an early red flag for Rett syndrome.
01Research in Context
What this study did
The team recorded babies during play at 9, 10, and 11 months.
They compared infants later diagnosed with Rett syndrome to typically developing peers.
From each hour-long tape they counted every canonical babble, then divided by total sounds to get the CBRUTTER ratio.
What they found
Infants with Rett syndrome had a CBRUTTER of 0.15 or lower.
Typical babies were above that line.
Fewer real babbles means fewer well-formed syllables ready for first words.
How this fits with other research
McCauley et al. (2018) first noticed odd timbre and sing-song in one Rett baby; the new study shows the problem is measurable by 9 months.
Leaf et al. (2012) proved untrained adults can hear the difference; Kremkow et al. (2022) now give you a clear cut-off to write in reports.
Raslear et al. (1992) listed eye gaze as the top pre-linguistic tool in older girls; the current work says check babbling before you lose it.
Why it matters
You can flag Rett risk with a simple 30-minute language sample.
If CBRUTTER is 0.15 or below at the nine-month check, refer to neurology and start family support.
Early ID buys time for genetic testing, seizure watch, and planning AAC before the regression phase hits.
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02At a glance
03Original abstract
Rett syndrome (RTT) is a rare, late detected developmental disorder associated with severe deficits in the speech-language domain. Despite a few reports about atypicalities in the speech-language development of infants and toddlers with RTT, a detailed analysis of the pre-linguistic vocalisation repertoire of infants with RTT is yet missing. Based on home video recordings, we analysed the vocalisations between 9 and 11 months of age of three female infants with typical RTT and compared them to three age-matched typically developing (TD) female controls. The video material of the infants had a total duration of 424 min with 1655 infant vocalisations. For each month, we (1) calculated the infants' canonical babbling ratios with CBRUTTER, i.e., the ratio of number of utterances containing canonical syllables to total number of utterances, and (2) classified their pre-linguistic vocalisations in three non-canonical and four canonical vocalisation subtypes. All infants achieved the milestone of canonical babbling at 9 months of age according to their canonical babbling ratios, i.e. CBRUTTER ≥ 0.15. We revealed overall lower CBRsUTTER and a lower proportion of canonical pre-linguistic vocalisations consisting of well-formed sounds that could serve as parts of target-language words for the RTT group compared to the TD group. Further studies with more data from individuals with RTT are needed to study the atypicalities in the pre-linguistic vocalisation repertoire which may portend the later deficits in spoken language that are characteristic features of RTT.
Journal of developmental and physical disabilities, 2022 · doi:10.1177/08830738050200090701