Babies who move their eyes more often than their peers at the age of 6 months are more likely to meet criteria for autism spectrum disorder (ASD) as children, researchers have found.
Babies constantly make fine eye movements that are barely visible. The frequency of these movements has been thought to show how engaged an infant is with what they are looking at, and how quickly they process what they are seeing.
In this study, researchers used eye tracking technology to measure 104 babies aged 6-8 months at high or low familial risk for ASD. They examined how often babies moved their eyes when scanning a static image. They found that typical babies moved their eyes about twice a second. However, those babies who later were diagnosed with ASD tended to move their eyes more frequently – about 3 times a second. These babies were scanning the image more rapidly than their peers.
The researchers hope that these findings may in future help contribute to better ways of identifying babies with early signs of possible behavioural difficulties. But they stress that the research is at an early stage and eye movement alone is a far from reliable indicator that a child may later be diagnosed with ASD.
"We are still at a very early stage in understanding what these results may mean,” said the study’s lead author, Dr Sam Wass. “Adults with ASD can sometimes process visual information more rapidly than other people, and perhaps that was happening for infants in our study. Alternatively, it could be that these babies need a higher level of stimulation, so they move their eyes more frequently to get more stimulation. Or it could be that when they look at something they are not engaging with it in the same way as other children tend to."
In addition, the babies at high risk for ASD showed little variation in the frequency of their eye movements. Earlier studies have shown that when looking at a new image or scene, most adults show an initial ‘scanning’ phase characterised by frequent eye movement, followed by a phase of less frequent eye movements. This study showed a similar pattern in the babies at low risk of ASD. However, the babies in the group with a higher risk of ASD showed far less variation across time with highly consistent and repetitive timing of their eye movements.
Professor Hugh Perry, chairman of the Medical Research Council’s Neurosciences and Mental Health Board, which funded the works, said: "This study is part of a growing body of research on the early development of infants later diagnosed with ASD. Up until now, few studies have been able to identify any behavioural signs of ASD in infants as young as 6 months. This research suggests that eye tracking technology could be used to reveal more subtle changes that might give us some important clues as to what might be causing autism in the developing brain.”
The project, which was hosted at Birkbeck, University of London, is part of the UK BASIS study of infants with older siblings with ASD, and is funded by the UK Medical Research Council and a consortium of charities led by research charity, Autistica.
Dr Simon Wallace, research director at Autistica, added: “This research is adding to growing evidence about very early brain and behavioural differences that indicate whether an infant is at elevated risk for autism. Parents are often aware that their child is behaving differently from a young age but still wait too long to receive a diagnosis and we hope that this research will ultimately lead to improved identification and diagnosis of autism.”