Children and adolescents with fragile X syndrome struggle significantly more with reading social cues and understanding other people’s emotions than those with autism or typical development, new research has found. The findings, published in the Journal of Neuropsychology, shed fresh light on the social challenges facing young people with one of the most common genetic causes of intellectual disability, and may help shape more targeted support strategies.
Fragile X syndrome affects roughly one in 4,000 males and one in 8,000 females. It is caused by a change in a gene on the X chromosome and is closely linked to autism spectrum disorder, with the majority of those affected showing some degree of autism-related traits. Despite this overlap, researchers have long suspected that the social difficulties in fragile X syndrome may have distinct roots.
A team based at Erasmus University Medical Center in Rotterdam studied 34 children with fragile X syndrome, 30 with elevated autism symptoms, and 27 typically developing children aged 6 to 18. Using eye tracking technology, the researchers measured how long each child looked at faces and eyes during a series of tasks involving emotional images paired with matching or mismatching audio. They also assessed Theory of Mind, the ability to attribute thoughts, beliefs, and intentions to others.
Children with fragile X syndrome spent considerably less time looking at faces and particularly the eyes compared to both the autism symptom group and typically developing peers. This reduced attention to socially important facial features was independent of age and general cognitive ability, suggesting it reflects something specific to the condition rather than simply a lower intellectual level.
When children were shown mismatched emotional cues, for instance a happy face paired with an incongruent audio stimulus, children with fragile X syndrome showed a notably weaker pupil response than those with autism. This muted physiological reaction suggests their brains may process emotionally conflicting information differently, with less automatic arousal in response to social surprises.
Performance on the Theory of Mind tasks also revealed that children with fragile X syndrome scored lower than both comparison groups. The gap was most pronounced in verbal tasks measuring the ability to reason about false beliefs, intentions, and figurative language, core capacities involved in everyday social interaction and communication.
The researchers note that reduced visual attention to emotionally relevant faces in early childhood may limit opportunities for social learning, potentially creating a cascade of developmental difficulties. Early identification of these patterns could help clinicians and families intervene sooner, before social cognitive difficulties compound over time.
While the study is exploratory and involved relatively small groups, it is among the first to directly compare eye gaze behaviour and implicit emotion recognition across fragile X syndrome, autism, and typical development in children and adolescents. The authors call for larger studies and trials of targeted early interventions, noting that approaches proven effective in non-syndromic autism may not translate directly to children with fragile X syndrome, who tend to have lower cognitive levels and more constrained social learning capacity.