Mood impacts confidence through biased learning of reward likelihood

BackgroundIntuitively, emotional states guide not only the actions we take, but also our confidence in those actions. This sets the stage for subjective confidence about the best action to take to diverge from the actual likelihood and, clinically, may give rise to over-confidence and risky behaviours during episodes of elevated mood and the reverse during depressive episodes. Whilst computational models have been proposed to explain how emotional states recursively bias perception of action outcomes, these models have not been extended to capture the impacts of mood on confidence. Here we propose a computational model that formalises confidence and its relationship with learning from outcomes and emotional states. MethodsWe collected data both in a laboratory context (n=35) and in pre-registered online replication (n=106; https://osf.io/ygc4t). Participants completed a two-armed bandit task, with learning blocks before and after a mood manipulation in which participants unexpectedly received (positive mood induction) or lost (negative mood induction) a relatively large sum of money. Participants periodically reported their decision confidence throughout the task. We examined the extent to which the mood manipulation biased their confidence, predicting that positive and negative moods would lead to over- and under-confidence, respectively. We further predicted that this effect would be stronger in participants with greater propensity towards strong and changeable moods, measured by the Hypomanic Personality Scale. Moreover, we formalized a computational model in which confidence emerges as the difference between the perceived likelihood of reward for the available options. In this model, mood indirectly biases confidence through recursively biased learning of the reward likelihoods for the available options and not from simply shifting overall confidence up or down. ResultsIn both experiments, we confirmed that moods impacted confidence in the hypothesised direction; absent of any differences in participants objective performance, average confidence was higher following positive mood induction, and lower following negative mood induction. This effect was larger in participants with higher levels of trait hypomania. Intriguingly, we found that the effect of mood on confidence emerged in concert with learning. Indeed, whilst the shift in mood was greatest immediately post-mood manipulation and returned to baseline by the end of the learning block, the effect of mood on confidence gradually accumulated over learning trials, peaking at the end of the block. These dynamics were captured by simulations of a "Moody Likelihood" model. Empirically, this model simultaneously accounted for the effects of mood on choices, mood states and confidence through a mood bias parameter. ConclusionWe present a unified model in which moods recursively bias reward learning and, consequently, confidence in decision making. Moods fundamentally bias the accumulation of reward likelihood, rather than directly biasing decision confidence. Clinically, these findings have implications for understanding two core symptoms of mood disorder, suggesting that both perturbed mood and confidence about goal-directed behaviour arise from a common bias during reward learning.