Autism (ASD) is a neurodevelopmental disorder that affects around 1% of the population , and is characterized by impairments in social communication, as well as repetitive / stereotyped behaviors .
While the disorder exists on a spectrum (meaning that the severity of the symptoms can vary greatly), many autistic individuals face various challenges throughout day-to-day life .
Attempts to mitigate the negative impacts of the disorder have only had success (albeit, limited) when introduced at an early stage of development , which has incentivized finding ways to diagnose ASD at a similarly young age.
The range of abilities that are available to infants is of course limited, in both autistic and typically developing populations, so attempts to diagnose ASD in a non-invasive manner have relied on those skills that are available. This is where eye tracking comes in.
The use of eye tracking
Researchers have investigated how attentional biases in social situations – measured through eye movements – can differ between ASD children and typically-developing children. As individuals with ASD typically have some level of social communication difficulties, the theory is that this is reflected in where they look too.
The ultimate goal of this research is to uncover a pattern of behavior that can be uncovered by eye tracking devices, and can reliably predict the development of ASD later in life.
While such a predictor still awaits discovery, great progress has been made. The text below describes some of the pivotal research into ASD and eye tracking, and the direction that this research is heading.
One of the typical experimental setups for investigating attention in ASD is to use a social setting (which can be completed either on a screen, or in a real-life scenario). This typically features the recording of eye movements using an eye tracker, while the participants view various video recordings.
There have been a variety of stimuli that have been used. Some have used elements of biological motion (shapes that represent a walking person, compared with those same shapes in random positions, for example ), others have used paired visual preference paradigms (social scenes on one side of a screen, and shapes or patterns on the other ), and others have simply looked in detail at responses to social scenes.
A prototypical example comes from Klin et al in 2002 , who showed that adolescents and adults with ASD were less likely to fixate on the eye region of characters shown in a movie. This suggested that central characteristics of ASD could be split into smaller, more quantifiable components, and used to study ASD further.
Similar research with similar results has been repeated many times [8, 9, 10, 11], showing the consistency and robustness of the finding that gaze patterns differ in individuals already diagnosed with ASD.
Klin’s pivotal piece of research spurred further investigations into the viewing behavior of infants, in a hope to identify such robust, and quantifiable, predictors of ASD at an early age as possible.
Jones et al
Jones et al  used eye tracking to investigate where both typically developing and autistic children (2-year-olds) looked while watching videos of adults engaging in play-like behavior. They found that the autistic children were much less likely to view the eyes (similar to the Klin study), but that they were more likely to view the mouth of the actors.
Hosozawa et al
In contrast to this, Hosozawa et al  in a similar study didn’t find any reduction in viewing of the eyes, or an increase of looking at the mouth, but instead found a more heterogeneous viewing pattern among the ASD sample. This suggested that the viewing behavior wasn’t specialized, but instead evenly spread around the entire scene.
Young et al
In one of the first studies that attempted to use these findings to determine the potential later development of ASD, Young et al. (in 2009)  used eye tracking to investigate the viewing patterns of social scenes in 6-month-old children (that were at either a low or high risk for ASD).
In contrast to the expectations, reduced eye gazes were not associated with the later development of ASD (although the proportion of the sample that went on to develop ASD was too small to state this definitively ).
Elsabbagh et al
Adding further complexity to the understanding of early development of attention in ASD, Elsabbagh et al  completed a similar study with face orienting. By presenting different visual stimuli (some were images of faces, some were other objects), and recording which gained the most attention, they found that all children – irrespective of later ASD diagnosis – preferentially attended to the faces.
Shic et al
In 2014, Shic et al  used a similar approach as Young et al, but with a larger sample, finding that ASD was more likely to develop in 6-month olds who exhibited a reduced overall viewing time of the presented social scenes. Furthermore, they found that when these children viewed faces, they tended to focus on the features of the face.
This has intensified the race to find a reliable biomarker of ASD, by showing that identifiable components can be used to help understanding of the development of ASD.
While eye tracking of young infants has yielded encouraging results, it is also clear that more work needs to be done to delineate more accurate predictors of later ASD development. This could be helped by introducing other forms of measurement, as combined data sources could help verify each other .
This is best exemplified by the JAKE study , which uses eye tracking and a variety of other biometric methods to identify early biomarkers of ASD. An EU led study  has also embraced similar methods and is currently in initial phases (although is more focussed on developing personalised treatment methods of ASD than early diagnosis).
As these multimodal research studies are still ongoing, we can look forward to a clearer and more complete understanding of ASD, and how treatments can help improve the lives of those affected.
I hope you’ve enjoyed reading about the ways in which eye tracking technology is being used to advance the understanding of ASD. If you’d like to learn more about eye tracking can be used in research, download our free guide below.
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