Optimism bias, judgment of severity, and behavioral change during two stages of the pandemics in China.

We investigated the factors and consequences of optimism bias during two critical periods of the COVID-19 outbreak in China. In February 2020, we conducted Study 1 (N = 4313) to examine the initial outbreak. The findings revealed that individuals exhibited optimism bias toward COVID-19. Additionally, the number of newly confirmed and suspected cases positively influenced optimism bias. Later, in December 2022, we conducted Study 2 (N = 1767) to explore the Omicron outbreak. The results indicated that optimism bias persisted, albeit to a lesser extent. In this study, the number of infections among participants' social relations negatively predicted optimism bias, while the judged severity of COVID-19 consequences positively predicted it. Notably, optimism bias can attenuate the positive prediction of anxiety by perceived severity, while also positively predicting protective behavior by mediating the relationship between perceived severity and protective actions. This study highlights the beneficial role of optimism bias, both physically and psychologically, during the COVID-19 pandemic.