Abstract
Why do individuals tend to discount bad news when making judgements about the likelihood of future events? In this short review, we explore recent research findings regarding this frequently observed and replicated phenomenon - optimism bias - with particular attention on how this bias affects the way individuals update or revise their beliefs. We begin by highlighting five interrelated frameworks for understanding optimism bias (utility maximization, active inference, dual systems, cognitive immunity, predictive processing). We then examine findings from affective and clinical domains that indicate that people with depression and other psychiatric disorders, as well as acutely sad or anxious individuals, have dampened optimistic bias when updating beliefs in response to good news. Finally, we consider the neural underpinnings of these phenomena through the free energy principle and discuss implications for clinical interventions and future research.