The Effects of Negative Affect and Dispositional Pessimism on Decision-Making Under Ambiguity

Negative affect has been shown, in both humans and non-human animals, to bias decision-making under ambiguity away from so-called 'optimistic' responses that can yield higher rewards but also risk greater losses. The judgement bias task, a cognitive task that uses ambiguous stimuli to measure such decisions as indicators of affective state, has successfully been translated from humans to animals and back again. However, questions remain regarding how exactly affect influences 'optimistic' or 'pessimistic' decisions, and the extent to which dispositional pessimism also influences these decisions. To further understand links between affect and decision-making, we carried out a judgement bias task in humans and measured self-reported affect and dispositional pessimism. In a pre-registered online experiment, participants completed questionnaires assessing anxiety, depression, and pessimism, and undertook a judgement bias task. Our results mirrored previous findings showing that self-reported negative affect is associated with negatively-biased decision-making under ambiguity; individuals who reported higher anxiety and depression made a significantly lower proportion of 'optimistic' responses to ambiguous stimuli in the judgement bias task. However, we did not find sufficient evidence to reject the null hypothesis that self-reported dispositional pessimism is associated with 'pessimistic' responses in the task. Drift-diffusion modelling revealed that the more negative (less 'optimistic') judgement bias associated with self-reported anxiety and depression, could be explained by a bias generated during the decision-making process, represented by a lower drift rate. But due to high comorbidity, we were unable to determine whether negative judgement bias is driven primarily by anxiety or depression.