Korsakoff's syndrome (KS) is a neuropsychiatric disorder, caused by vitamin B1 insufficiency. KS is characterized by severe declarative amnesia. Often, also executive disorders are present. Emotion recognition and theory of mind are gold-standard measures of social cognition. Moral decision making is often assessed by means of moral dilemmas. Surprisingly social cognition and moral decision making has received hardly any attention in research on KS, although the severity of behavioural problems in KS suggest possible problems in both domains. The aim of this study was therefore to broadly assess social cognition and moral decision-making capacities in patients with KS.

20 KS patients and 20 age-, education-, and gender-matched healthy controls were assessed on standardized tests for social cognition, namely the mini-Social Cognition and Emotional Assessment battery (mini-SEA), and a specialized version of the Sally-Anne Test. Moral decision making was assessed by means of the Moral Behaviour Inventory (MBI) for everyday moral dilemmas, and ten cartoons of abstract moral dilemmas. For moral decision making, “yes” and “no” responses were scored, together with a scoring for moral reasoning according to the Kohlberg stages of moral maturity.

KS patients have large impairments in both cognitive and affective aspects of social cognition. Their ability to recognize emotions, take the perspective of others, and understand socially awkward situations is vastly compromised. While KS patients were able to replicate the Sally Anne storyline, their task performance was on chance level. Regarding moral decision making, there was a tendency to more frequently carry out the moral dilemma. Moral maturity, as indexed by means of their reasoning behind the decision was of a lower level. Of interest, moral immaturity could find its origin already before the onset of the KS diagnosis, as suggested by elevated premorbid levels of delinquent behavior.

Both social cognition and moral decision making are compromised in KS patients. Specifically social cognitive disorders are the direct result of KS, and are likely to strongly relate to social and neuropsychiatric issues in KS. Moral decision making was more likely to be already of a lower level of maturity, based on a strong relationship between premorbid delinquency and moral immaturity in KS patients. This study highlights the importance to properly index social cognition in neuropsychological assessments for individuals with a possible KS diagnosis