Anxiety is associated with elevated self-report of aversion to uncertainty and ambiguity. However there has been relatively little attempt to characterize the underlying mechanisms. Over recent years, computational modelling has been used to advance our understanding of human decision-making and the brain mechanisms that support it. This approach can help us to formalize and understand how choice behaviours can be optimally adapted to different situations and the ways in which individuals may deviate from optimal behaviour.
In everyday life, our decision-making often takes place under some form of uncertainty. We can distinguish ‘first-order’ uncertainty which occurs when a given action only leads to a given outcome on a proportion of occasions from ‘second-order’ uncertainty, which describes uncertainty regarding the action-outcome contingency itself. Two sources of second-order uncertainty are contingency volatility and contingency ambiguity. In experiment 1, we manipulated contingency volatility and revealed that elevated trait anxiety is linked to a deficit in adjusting probabilistic learning to changes in volatility and also to reduced peripheral (pupil dilation) responses to volatility. In experiment 2, through bifactor modelling of Internalizing symptoms and hierarchical modelling of task performance, we determined that this difficulty in optimizing probabilistic learning under volatility is common to both anxiety and depression. In experiment 3, we investigated another source of second order uncertainty. Here, we manipulated the level of ambiguity – or missing information – present on each trial. High trait anxious individuals showed elevated ambiguity aversion, being especially sensitive to increases in the amount of missing information when choosing between two options. Analysis of fMRI data revealed that participants show elevated activity in the dorsal anterior cingulate and inferior frontal sulcus at time of choice on trials with high missing information when they subsequently engaged with versus avoided the ambiguous option; this pattern was strongest in high trait anxious individuals. One possibility is that these frontal regions support rational evaluation of alternate actions as opposed to simple heuristic-based avoidance of options characterized by high second-order uncertainty.