From babbling to babytalk: how babies lip-read

This article in PNAS caught my attention the other day. Scientists in Florida tracked the eye gaze of 4-12 month babies, which covers the period of the first experimental babbling through to proper speech development. This is timed well with my recent blogpost on the topic of babbling.

The researchers found that, at 6 months, infants switch from focussing on their carer’s eyes to focussing on their mouth. This, the authors suggest, is so that the baby can pick up visual clues of how to start to form words: in essence, lip reading. At 1 year of age, when infants have started to master their word formation, they switch back to gazing at their carer’s eyes, which the authors think is to start to engage in social cues that form part of our ability to communicate socially.

The really interesting finding is that children who develop autism are more likely to stay focussed on the mouth at 1 year of age. The first question that hit me was the old ‘chicken-and-egg’ conundrum and how to separate cause from effect. Are some infants more likely to develop autism because they are less able to switch from gazing at the mouth to the eyes (due to some other underlying reason) or do some infants gaze more at the mouth than the eyes because they are autistic? In other words, does autism cause mouth-gazing or does mouth-gazing cause – or, at least contribute to – autistic behaviour? 

It’s another avenue to explore in trying to understand this complex developmental disorder (and it is complex). Either way the cause-and-effect lies, it could give doctors an early sign that a child will be diagnosed with autism later on, which should help in the support and treatment that those infants receive.

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