When you’re speaking to an infant, those big, baby eyes are paying close attention to your lips—and learning, according to a new study released in January.
The two-year study, a first of its kind, found that "infants shift their focus of attention to the mouth of the person who is talking when they enter the babbling stage and that they continue to focus on the mouth for several months thereafter until they master the basic speech forms of their native language," said lead author David Lewkowicz, a professor of psychology within the Charles E. Schmidt College of Science at Florida Atlantic University, in a statement.
"In other words, infants become lip readers when they first begin producing their first speech-like sounds," he added.
In the study, Lewkowicz and doctoral student Amy Hansen-Tift tested groups of infants between 4-months-old and one-year-old by showing them videos of women speaking in either English, which was the baby’s native language, or Spanish, which was not the baby’s native language.
As the babies watched the videos, researchers recorded their eye movements using an eye-tracker device. Babies in the "babbling stage" initially shifted attention to the women’s mouths, showing that infants engage in lip-reading, researchers said.
Researchers then concluded that the subsequent shift of focus from the mouth to the women’s eyes reflected the development of a native-language expertise. A persistence of lip-reading was seen in response to non-native language.
Researchers have pointed to this study as a potential new way to diagnose autism at an earlier age in babies. Now a diagnosis can be made at around 18 months, according to researchers, and one of the characteristics of autism is that by 2 years old autistic children continue to focus their attention on a speaker’s mouth whereas developing children focus on the eyes.
"Contrary to typically developing children, infants who are as yet undiagnosed but who are at risk for autism may continue to focus on the mouth of a native-language talker at 12 months of age and beyond," Lewkowicz said. "If so, this would provide the earliest behavioral confirmation of impending developmental disability and would give clinicians an early start on intervention procedures."
This study, which was published in the Proceedings of the National Academy of Sciences, was supported in part by grants from the National Science Foundation and the National Institutes of Health.