Working definitions, subjective and objective assessments and experimental paradigms in a study exploring social withdrawal in schizophrenia and Alzheimer's disease

•Discussion of working definition of social withdrawal in neuropsychiatric diseases.•Selection of subjective and objective rating scales for assessing social withdrawal in specific neuropsychiatric diseases.•Selection of MRI and EEG paradigms for studying brain circuitry and mechanisms involved in social withdrawal.•Selection of complementing behavioral paradigms and addition of a digital phenotyping tool.