Comparison of face attention bias in adults with ASD, ADHD, or comorbid ADHD+ASD

Faces are special for humans. This importance is reflected in increased relative attention to faces, referred to as face attention bias (FAB). This preregistered study investigated FAB transdiagnostically in two neurodevelopmental disorders associated with social symptoms, autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). We assessed exogenous selective attention to faces using a dot-probe paradigm in adults with ASD, adults with ADHD, adults with both and non-clinical comparison adults. While comparison adults showed FAB as expected, adults with ASD did not. Yet, the between-group difference in FAB was not credible, contrary to our hypothesis. Critically, adults with ADHD but no ASD showed increased FAB, suggesting heightened exogenous selective attention towards faces. This increase was not reflected in oculomotor behaviour, indicating covert attentional mechanisms. Adults with comorbid ASD and ADHD did not show increased FAB. Saccades were produced faster towards face-cued targets across all groups, but no significant interaction with group emerged regarding oculomotor behaviour. These findings unveil an attentional signature in ADHD: a heightened bias for faces possibly connected to social symptoms. Furthermore, they highlight the nuanced and distinct attentional profiles in different neurodevelopmental disorders, underscoring the critical need to understand shared and distinct mechanisms of ASD and ADHD.