Declan Nambu is 8 months old. He is learning to talk by listening and looking at his mother.

“Around 6 months of age, when babies begin to babble and begin to produce their first human speech sounds, they begin to shift their attention to the mouth of their social partners. So when someone is speaking to them they begin to look at their mouth,” Florida Atlantic University professor David Lewkowicz said.

At FAU’s Baby Lab, researchers studied more than 200 infants for about two and a half years.

Infants ranging in ages from 4 to 12 months were shown videos of women talking while their focal points were recorded with an eye-tracking device. The findings were just released in the Proceedings of the National Academy of Sciences.

Four-month-olds focus primarily on the eyes when someone is talking, but that changes.

“As babies are learning how to speak they become lip-readers, they begin to lip-read, and once they master the basic sounds of their own speech, of their own language, they no longer have to look there,” Lewkowicz explained.

Nambu is still in the lip-reading stage. The new research indicates he will return to focusing on eyes when he turns a year old. Lewkowicz says findings suggest if that shift does not happen by 14 months, “that could be a sign of impending difficulties, developmental difficulties, one of them being autism.”

Autistic children have been found to focus their attention on the mouth of the talker at age two. The new findings which show that the shift to the eyes happens around age one means there is a possible way to detect autism and begin interventions earlier.