Hidden Markov modeling is a powerful lens for observing hidden patterns in complex behaviors. In the study of autism, it has allowed scientists to analyze how children look at faces over time, revealing important differences in patterns of social attention. This technique not only provides insights into how autism affects visual perception, but also opens doors to new forms of diagnosis and intervention.
One of the most common difficulties faced by children with autism is reduced social attention, that is, the difficulty focusing on faces during social interactions. This behavior has a profound impact on the social development of these children, since the human face is one of the main sources of social information, such as emotions and intentions.
Although this characteristic is well known, little is known about how social attention develops over time in children with autism and how it differs qualitatively from neurotypical children.
To investigate this question, the researchers used a cutting-edge approach called hidden Markov modeling.
This technique analyzes complex patterns of behavior, such as eye movements, allowing us to observe how children visually process social information.
Hidden Markov modeling is a mathematical and statistical technique used to analyze patterns and predict behavior in complex systems. It is especially useful when we want to understand processes that change over time and whose internal states cannot be observed directly, but can be inferred from visible data.
Despite the complicated name, the concept can be explained in an accessible way.
Imagine that you are watching a play, but the curtains are closed and you can only hear sounds coming from the stage.
From these sounds, you try to guess what is happening: a conversation, an action scene, or a quiet moment. In this example, the events on stage (scenes) are the hidden states, you cannot see them directly. The sounds you hear are the visible observations, the data you collect.
Hidden Markov modeling helps you build a model to connect the sounds (observations) with what is likely to be happening on stage (hidden states). It does this based on probabilities, that is, using the chances that a certain sound is related to a specific scene.
The study involved 280 children with autism and 119 neurotypical children, all between the ages of 6 and 11. Each child participated in three social eye-tracking sessions conducted at three different time points: at baseline, six weeks later, and finally 24 weeks after the first session.
During testing, the scientists identified two main eye movement patterns that were consistent across participants.
The first was called the focused pattern, in which children focused their gaze on small areas of the face, such as the eyes or mouth. This pattern indicated a high initial sensitivity to relevant social information, such as facial expressions or communicative intentions.
The second pattern was called the exploratory pattern. In this case, the children’s gaze was distributed more broadly, including larger areas of the face and often non-social regions, such as the surrounding environment. This pattern was less effective at capturing social information, since participants did not quickly fixate on key parts of the face.
The results showed that children with autism were more likely to adopt the exploratory pattern, while neurotypical children predominantly exhibited the focused pattern.
This difference was observed across all social perception tests and at all three time points, suggesting that the exploratory pattern is a prominent and persistent characteristic in children with autism.
In addition, the eye movement pattern observed in children with autism was associated with specific clinical characteristics, such as difficulties in facial recognition, greater severity of autism symptoms, and impaired adaptive function. This means that children who had more difficulty focusing on faces also had greater challenges in social skills and recognizing facial expressions, which are essential for interpersonal interactions.
The data suggest that a decreased likelihood of fixating on faces early in visual processing may be a key feature of autism. This difficulty is not only related to social behavior, but may reflect a decreased visual sensitivity to facial information.
In other words, the brains of children with autism appear to process social information differently from the earliest moments of observation. These findings have important implications for autism interventions and treatments.
Understanding social attention patterns could help develop targeted therapies that encourage early focus on important facial regions, such as the eyes. This could improve social perception and help develop interaction skills.
In addition, the study provides new clues to identify autism earlier, enabling more targeted and personalized interventions.
Finally, by demonstrating that children with autism process faces differently over time, this study reinforces the importance of investigating not only behavioral differences, but also the neurocognitive basis of these differences. It opens the door to future advances in diagnosis, treatment, and understanding of social dynamics in autism.
READ MORE:
Spatiotemporal Eye Movement Dynamics Reveal Altered Face Prioritization in Early Visual Processing Among Children With Autism
Jason W. Griffin, Adam Naples, Raphael Bernier, Katarzyna Chawarska, Geraldine Dawson, James Dziura, Susan Faja, Shafali Jeste, Natalia Kleinhans, Catherine Sugar, Sara Jane Webb, Frederick Shic, and James C. McPartlandÂ
Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 3 September 2024
Abstract:
Reduced social attention—looking at faces—is one of the most common manifestations of social difficulty in autism that is central to social development. Although reduced social attention is well characterized in autism, qualitative differences in how social attention unfolds across time remains unknown. We used a computational modeling (i.e., hidden Markov modeling) approach to assess and compare the spatiotemporal dynamics of social attention in a large, well-characterized sample of children with autism (n = 280) and neurotypical children (n = 119) (ages 6–11) who completed 3 social eye-tracking assays at 3 longitudinal time points (baseline, 6 weeks, 24 weeks). Our analysis supported the existence of 2 common eye movement patterns that emerged across 3 eye-tracking assays. A focused pattern was characterized by small face regions of interest, which had high a probability of capturing fixations early in visual processing. In contrast, an exploratory pattern was characterized by larger face regions of interest, with a lower initial probability of fixation and more nonsocial regions of interest. In the context of social perception, children with autism showed significantly more exploratory eye movement patterns than neurotypical children across all social perception assays and all 3 longitudinal time points. Eye movement patterns were associated with clinical features of autism, including adaptive function, face recognition, and autism symptom severity. Decreased likelihood of precisely looking at faces early in social visual processing may be an important feature of autism that is associated with autism-related symptomology and may reflect less visual sensitivity to face information.
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