Deficits in the knowledge of social norms and their correlates in Alzheimer's disease.

Objective: Compared to other components of social cognition, knowledge of social norms has received less attention in the scientific literature. While social cognitive and semantic memory deficits appear early in the course of Alzheimer's disease (AD), no study has examined knowledge of social norms at earlier stages of the disease. In addition, it is unclear whether the knowledge of social norms in AD is associated with socioemotional deficits, as may be seen in the behavioral variant of frontotemporal dementia (bvFTD). Method: This study included 136 participants with amnestic mild cognitive impairment (aMCI), 134 with AD, most of whom were younger than 65 years, 280 with bvFTD, and 361 older healthy controls (HC). All participants were selected from the National Alzheimer's Coordinating Center (NACC). They completed the Social Norms Questionnaire (SNQ), which assesses the tendency to break or overadhere to social norms. They also completed tests assessing executive, semantic, and socioemotional functions. Results: Between-group comparisons showed that individuals with AD and aMCI made significantly more Break and Overadhere errors than HC, while they demonstrated better social norms knowledge than individuals with bvFTD. In aMCI and AD, social norms overadherence errors were most consistently associated with executive functioning. In bvFTD, semantic memory was the most consistent correlate across all SNQ variables. Conclusions: These findings may help clinicians and researchers better understand social cognitive changes in patients, support the inclusion of social norms knowledge assessment within broader neuropsychological evaluations, and provide complementary insight into the cognitive correlates of social knowledge loss in major neurocognitive disorders.