ObjectiveAnorexia Nervosa (AN) is a serious disorder, with a mortality rate the highest of any psychiatric illness. It is notoriously challenging to treat and mechanisms of illness are not well understood. Reward system abnormalities have been proposed across theoretical models of the persistence of AN. Feedback learning is an important component of how reward systems shape behavior and we hypothesized that individuals with AN would show poorer learning from feedback. MethodsWe administered the acquired equivalence task to measure both learning from incremental feedback and generalization of that learning to novel stimuli. Participants were individuals with AN (n=36) before and after intensive weight restoration treatment and healthy comparison participants (HC, n=26) tested twice. Performance was assessed as accuracy during the Learning and Test phases, for both trained and novel stimuli. The relationship between task performance and eating disorder severity at baseline was also assessed. ResultsBoth before and after treatment, individuals with AN showed reduced learning from feedback in the Learning phase (F-3,F-180=2.75, p=.048) and lower accuracy during the Test phase (F-1,F-60=4.29, p=.043), as compared with HC. Individuals with AN did not differ from HC in accuracy for novel stimuli (F-1,F-60=1.04, p=.312), indicating no deficit in generalization. Decreased acquisition of feedback learning was associated with longer illness duration and with greater eating disorder symptom severity at baseline. ConclusionsIndividuals with AN show reduced learning from feedback or reinforcement, which may contribute to difficulties in changing maladaptive behaviors.