People tend to observe the left side of the face more closely. Photo: Albert Dera on Unsplash

Atypical gaze behavior in response to a face has been well documented in individuals with autism spectrum disorder (ASD). Individuals tend to explore the left side of a face first and for a longer time compared with the right side. This left visual field bias is suggested to reflect right hemispheric dominance for face processing. The finding has been noted in conditions associated with impaired social interaction, such as ASD. 

Eye tracking studies investigating visual behavior often rely on “areas of interest” analysis as a basis for gaze data analysis. With this method, the researcher manually defines areas in the stimulus space that are relevant to identify which among these (e.g., the eye region of a face) attract and hold the attention of the participants. Once the areas have been determined, gaze is classified as a dichotomous variable—the gaze that falls within the area’s borders is accounted for, while gaze registration falling outside is excluded from the gaze metrics. This type of analysis leads to great variability and is difficult to reproduce.

Researchers in Denmark and Sweden have developed a model that reveals a lateralization component of gaze patterns based on a concept called primary component analysis. Unlike the “areas of interest” approach, it uses recorded gaze data to define relevant attentional components before looking for clinical correlates. This allows for the discovery of novel areas of interest that might otherwise go unnoticed.

“By using this method, we automatically identify components in the gaze data that determine areas of the stimuli showing relevant gaze patterns for the recorded data,” the researchers noted.

The study applied the analysis to a clinically diverse sample of 111 psychiatric outpatients, with the goal of generating gaze components corresponding to their clinical profiles. It also collected dimensional symptom scores of autism, attention deficit and depression. The team then used the components of the analysis to build a regression model linking them to psychometric scores relevant to the participants. The model explained the scores and used a feature selection method to select which components were most predictive for each score.

Given what is already known about the neural correlates of left visual field bias, the researchers suggested reduced lateralization in individuals with higher autism scores may therefore reflect the reduced activation in the right hemisphere. Similarly, those who had higher values on the depression score exhibited less gazing to the left side of the face stimuli than those with lower depression scores. The regression analysis revealed that the depression score had an effect on the left-right gaze component, even after correcting for the autism score. The team acknowledged that they are not aware of any prior research showing a link between depressive symptoms and a reduction in left visual field bias during face gaze.

In short, gaze analysis is allowing brain researchers to understand how individuals with autism and/or depression process visual stimuli in a way that yields clinical associations that may be relevant to doctors providing their care.