Most autistic children are not diagnosed as such until they are three years old, and by then valuable time has already been lost. But Patricia K. Kuhl, a neuroscientist at the University of Washington, and her colleagues have discovered that certain neural and behavioral differences can be spotted in autistic children as young as two. The researchers plan to test whether they can similarly distinguish babies at six months of age. The goal is to create a screening tool that could identify a risk of autism as early as possible, “when the brain is so plastic,” Kuhl says. “That's the time to get in and try to intervene.”

Children's brains are wired for language by roughly their third year. Their language aptitude depends significantly on their ability to detect phonetic cues during those years as well as to attend to adult voices, notably their mother's. Kuhl's group compared these two skills in autistic children and in typically developing children between the ages of two and four.

The autistic preschoolers' brains showed no response to a consonant change in a string of identical sounds (the phonetic cue). And they overwhelmingly preferred a computerized, nonspeech warble to samples of “motherese”—the expressive and elongated speech that mothers often use with young children, which, other research has shown, enhances language learning.

Kuhl thinks that certain infants will also show a clear preference for either motherese or the computer warble. If further research indicates that choosing a warble is predictive of autism, “then you would start really following those kids,” Kuhl says.