Early detection of autism in infants is often indicated through various biomarkers. Now, research from the Marcus Autism Center of Children’s Healthcare of Atlanta and the University of Memphis indicates boys produce significantly more vocalizations known as protophones than girls – a difference that is more pronounced in boys at high risk for autism in the first six months after birth.
“Parents of children at high risk of autism should be aware their children could exhibit differences in behavior from the earliest months of life,” said Gordon Ramsay, PhD, Director of the Spoken Communication Laboratory at the Marcus Autism Center. “This has been consistently demonstrated in results from biomarkers like eye-tracking and neuroimaging. Now our research shows this difference also shows up in vocal measurements in boys.”
Dr. Ramsay and his team recorded the daylong home vocalizations of 100 infants during the first 12 months of life. The recordings were then analyzed by D. Kimbrough Oller, PhD, Chair of Excellence in the School of Communication Sciences and Disorders at the University of Memphis, to determine if there were differences between boys and girls, and those at high and low risk for autism (with high risk defined as having a sibling with autism).
After a five-year collaboration funded by the National Institutes of Health, Dr. Oller and Dr. Ramsay found boys produce significantly more protophones, the precursors to speech including vowel-like sounds, squeals and growls, than girls, and this difference was even more pronounced in infants at high risk for autism at the beginning of the first year. The team published their findings in Current Biology.
“Both high and low risk groups show the advantage of boys in the rate of vocalizations being produced,” said Dr. Oller. “This is a big surprise. The presumed difference between boys and girls in language later in life in general is small, and it favors girls, but the male protophone advantage we observed in the first year is more than four times larger than the commonly reported female language advantage.”
Dr. Ramsay and Dr. Oller noted these differences primarily occur between zero and six months of age, while the female advantage begins after the first year with slightly larger vocabulary sizes and other female language advantages continuing throughout life. They discovered while quantity of protophones is higher in boys, quality is not, suggesting this finding may not be related to language development alone. From an evolutionary perspective, they hypothesize this difference may be due to boys’ higher risk of medical complications in the first year, as boys are 60% more likely to be born prematurely, their infant mortality rate is 30% higher, and they are known to be at greater risk of autism from birth.
“Boys are known to be generally more vulnerable in the first year of life than girls, so these results may reflect the evolution of vocal signaling strategies eliciting parental care to buffer the elevated risk,” said Dr. Oller, who is also professor with the Konrad Lorenz Institute for Evolution and Cognition Research in Austria.
While the team is still exploring the implications of this unexpected finding, the exaggerated difference in boys at high risk for autism provides evidence for an early biomarker in pre-speech vocal behavior.
“If early protophone production is indeed a fitness signaling strategy with evolutionary origins, it is natural that differences between boys and girls would be more pronounced in infants at risk of autism, and more likely to elicit early concern from parents in ways that promote the health and survival of the child,” said Dr. Ramsay, who is also an Assistant Professor with the Emory University School of Medicine Department of Pediatrics.
Dr. Ramsay hopes these findings will encourage parents to seek treatment sooner, before their child’s first words, when the window of opportunity is greatest for shaping their child’s long-term health.