Understanding positive affect in Angelman syndrome: Smiling and laughter across comparison groups

Angelman syndrome (AS) is a neurogenetic condition marked by frequent smiling and laughter. Early descriptions portrayed these expressions as inappropriate or disconnected from context, but recent work has questioned this view. This study examined the emotional responses of children with AS to auditory, tactile, visual, and social stimuli and compared them to typically developing (TD) children and children with Autism Spectrum Disorder (ASD). Using Bayesian mixed-effects models, we analyzed behavioral ratings and Facial Action Coding System (FACS) data. Children with AS showed more frequent positive-expression behavior, but these elevations were selective rather than indiscriminate. All groups relied on a shared repertoire of smile- and laughter-related facial actions, with AS differing primarily in the intensity and frequency of these shared actions. These findings indicate that emotional expressions in AS are context-sensitive and grounded in meaningful environmental cues, challenging the notion that their positive affect is reflexive or aberrant.