Learning from disinformation

Reinforcement Learning studies how animals and humans adapt to their environment by learning from experience which actions maximize reward acquisition. Extant research has focused on situations where learners receive veridical reward-feedback. However, as social beings, much of the feedback we receive is provided by others. Critically, such feedback may be misleading because others might manipulate us based on their own –even if well-intended– interests. For example, a colleague might spare your feelings, expressing enthusiasm regarding your imminent Cosyne submission when, they actually find it superficial. A pressing question concerns behavioral adaptations when potentially misleading feedback is provided. We addressed this question using an online modified version of the two-armed bandit task, that informed participants (n=107) about reward-outcomes of their choices through “feedback agents” who occasionally lied (reporting a non- reward when the true outcome was a reward and vice versa). One agent always reported feedback truthfully, whereas three other agents varied in their unreliability, i.e., the proportion of trials in which they lied (15%, 30%, or 50%). Computational modelling of participants’ behavior revealed that credit assignment (i.e., the extent of value-update following reward feedback) increased as a function of feedback-reliability. Strikingly, we also found that while credit assignment for the always-truthful agent was symmetric (i.e., equal for positive and negative outcomes), unreliable feedback elicited a positivity bias such that credit assignment was greater for positive compared to negative feedback. Critically, this feedback-valence learning bias could not be accounted for by optimal Bayesian learning models. Exploratory analyses, aimed at relating learning-biases to mental health, suggest that obsessive-compulsive symptoms and paranoid thoughts are linked to a reduced learning sensitivity to feedback reliability. Our results can help explaining how learning from disinformation might contribute to deficits in mental health and social communication (e.g., political radicalization and belief in conspiracy narratives).