Babies as young as four months are able to recognise emotions in people's faces, according to a new study.
Scientists found that even before they start talking babies are able to pick up on "non-verbal" signals we use to communicate, such as the eyebrows being raised by a smile to indicate friendship.
By using near infrared light to take an image of brains of infants, researchers in London found that they use the same brain regions that adults do when they look at the gaze of another, a foundation for social interactions that appears critical for social development and might go wrong in conditions such as autism.
Dr Tobias Grossman, Prof Gergely Csibra, Prof Mark Johnson and colleagues at The Centre for Brain and Cognitive Development, Birkbeck, University of London, working with Prof Clare Ewell of University College London. report the study today in the Proceedings of the Royal Society, Biological Sciences.
Four-month-old infants took part in two scenarios in which a face either established mutual gaze or averted its gaze, both of which were followed by an eyebrow raise with an accompanying smile.
The team studied the blood oxygenation of the infant brain, as measured by near infra red light and also by a net of electrical sensors in a method called EEG that picks up brain waves.
They show that a gaze activates parts of the cortex, the rind of the brain, where the equivalent job of monitoring gazes is done by adults (the temporal and prefrontal cortex).
Babies can pick up on gaze, even when looking at a face sideways on. "In four -month-old babies we demonstrate very early specialisation, and indeed, an adult-like pattern of activation of the brain regions that process face-to-face social interaction," said Dr Grossman.
Studies in other labs already show that toddlers with autism have difficulty making eye contact. Dr Grossman says that future work will focus on how important this aspect of development is for social skills.
"The main goal of my work is to understand the brain mechanisms that underlie typical (healthy) social development. But I still hope that once we better understand healthy development that we can use this knowledge to look into what might go awry in neurodevelopmental disorders."
"We are not claiming it could diagnose autism - merely that it may prove a useful early warning signal," added Prof Johnson, whos work is backed by the MRC and Wellcome Trust.
Pioneering work by Prof Johnson at Birkbeck, which has one of the world's leading baby labs, has shown that infants are interested in faces and that newborn babies not only prefer to look at faces that have open eyes but also exhibit a strong tendency to attend to faces that engage them in mutual gaze as compared to averted gaze.
It has been argued that an early sensitivity to eye gaze serves as a major foundation for later development of social skills and that insensitivity to where another is looking could be an early sign of disorders such as autism.
"What we did not know before is which brain systems young infants use to process face-to-face communication and whether these brain systems and processes are similar to those employed by adults (i.e. whether they specialise early in development)," said Dr Grossman.
By comparison, the so-called fusiform face area, which enables us to recognise another person's face, takes up to a decade to develop this level of specialisation. This dovetails with a study that came out a few weeks ago in PLoS ONE where Dr Roberto Caldara at the University of Glasgow found that cultural differences cause us to look at faces differently.
Another brain scan study by Dr Jack Nitschke at the University of Wisconsin-Madison, published in the journal NeuroImage, found that when a new mother gazes at her baby, it's not just her mood that lights up - it's also a brain region called the orbitofrontal cortex associated with emotion processing, confirming what all mothers know: just looking at baby makes them happy.