The acoustics of a baby's cry may serve as one indicator of whether an infant will develop autism, according to a recent study conducted by University researchers.
"A major challenge in research in autism is how we can identify autism in early infancy," said Stephen Sheinkopf, assistant professor of psychiatry and human behavior and lead author of the study, published in the October issue of the journal of Autism Research. "We know that older children with autistic disorders often produce sounds in odd and unusual ways ... we wanted to measure this phenomenon in infants in the context of crying," he said.
Sheinkopf and his fellow researchers examined the naturally occurring cries of about 40 six-month-old infants, representing two subject groups. One group was identified as high-risk for Autism Spectrum Disorder because the subjects had an older sibling with the disease. The second group was identified as low-risk for autism because the subjects had no siblings who had the disorder, Sheinkopf said.
Recordings of the cries were made using a camcorder and microphone embedded in a vest worn by each infant at home, according to the study. Once recorded, the cries were categorized into pain-related and non-pain-related cries. The pitch of the cries was identified using a program specifically designed for the study.
When the researchers compared the pitches of the pain-related cries from both groups they found that the cries of the high-risk infants on average had a statistically significant higher pitch than the cries of low-risk infants, Sheinkopf said. In fact, the three infants in the high-risk group who did develop autism were the subjects with the three highest-pitched cries, he said. No statistically significant difference in acoustic features was found for the non-pain-related cries, according to the study.
"Atypical cry acoustics ... may serve as a positive symptom that, when combined with other indices of risk, may have additional value as a means to increase the accuracy of early identification efforts," the study states.
One of the study's major strengths was its "careful and systemic approach while using naturalistic observation," said Kelley Powell '06, post-doctoral psychology fellow at the Yale University Child Study Center, who was not involved in the study.
Most cry acoustic studies evoke cries systematically to gather data, Powell said. The experimental design of this study, in which cries were observed "naturalistically," was a new approach to collecting cry acoustic data, Powell said.
She recommended the researchers reevaluate the infants when they are 36 months old to see if the infants with Autism Spectrum Disorder still have a higher-pitched cry.
Identifying autism early in an infant's development would benefit the autism field of research by allowing specialists to initiate intervention measures earlier, Sheinkopf said.
Unfortunately, the dynamic between early identification and intervention is a "chicken and egg problem," he said. Currently, little to no treatment options are in place for high-risk infants under 12 months, he said. But early identification of high-risk children may inspire the development of treatment options for these infants, Sheinkopf said.
Sheinkopf and Powell both noted that the study's small sample size was a weakness. The biggest challenge was identifying prospective high-risk infants - a difficult task given that autism is not diagnosed until age two, Sheinkopf said.
"It's a first publication in this area," Sheinkopf said. "We need to follow up."
Powell said it was "surprising" there were more females in the at-risk group, as autism typically affects more boys than girls. For example, if an older sibling has autism, a younger brother has a one in four chance of developing the disease, while a younger sister's chance is one in nine, she said.
Since the initial study, Sheinkopf said he and his colleagues have been "replicating and extending" their work. The team joined forces with Professor of Engineering Harvey Silverman to develop a computer program that would hone their cry analysis technique.
Armed with the new and improved cry analysis program, Sheinkopf said the team is currently examining cries' phonation, or harmonic vibration of the vocal cords. "You can think of it as a tape recording with a lot of static in the background versus a tape recording without static," Sheinkopf said, describing the difference in phonation between high-risk and low-risk infants. The cries of high-risk infants are less clear and have more background noise, he said.
"We are looking at more variables, more frequencies to describe the cries, and piecing those different elements together to find patterns," Sheinkopf said.
The new cry analysis mechanism is a "useful tool" that the team looks forward to sharing with the research community at large, he said. Analysis of cry acoustics proves useful for other developmental disabilities and neurological impairments, including early infant brain damage and in utero drug exposure, he said.
When it comes to cry acoustics in relation to autism, Sheinkopf said the University's lab is one of the few doing this work. "Vocalization in autism is an area that has lain dormant, but is resurging," Sheinkopf said.