Despite substantial research on overall decision-making capacity levels in schizophrenia, the factors that cause individuals to make errors when making decisions regarding research participation or treatment are relatively unknown. We examined the responses of 84 individuals, middle-aged or older, with schizophrenia or schizoaffective disorder. We used a structured decision-making capacity measure, the MacArthur Competence Assessment Tool for Clinical Research, to determine the frequency and apparent cause of participants’ errors. We found that most errors were due to difficulty recalling the disclosed (...) information, particularly the study’s procedures, potential risks, and purpose. Errors attributable to concrete thinking, psychotic symptoms, or perceived coercion were rarer. These results suggest that informed consent procedures for this population might be improved by providing information in a way that facilitates learning and memory, such as iterative disclosure of the information, corrective feedback, and emphasis of key points of the study—for instance, its purpose, procedures, and potential risks. (shrink)