Optimistic bias in updating beliefs about climate change longitudinally predicts low pro-environmental behaviour.

We investigated the preregistered hypothesis that an optimistic bias in updating beliefs about climate change (i.e., integrating good news more than bad news) cross-sectionally (N = 109) and longitudinally (N = 407) predicts self-reported pro-environmental behaviour (PEB). To test this, we employed an experimental task in which participants were presented with multiple climate change scenarios and asked to update their beliefs after receiving scientific evidence. Additionally, we investigated whether biased belief updating and PEB could be altered by brief experimental interventions providing information on different aspects of climate change. Results show that optimistically biased belief updating did not predict PEB cross-sectionally, but did predict PEB 4 weeks later, while controlling for baseline levels of PEB. The experimental interventions did not significantly alter belief updating or increase PEB, although there were significant gender differences. The results suggest that an optimistic bias in belief updating longitudinally predicts low engagement in PEB, possibly because selectively integrating good news over bad news reduces the perceived urgency to take action. Yet the effect may be small and detectable only in sufficiently large samples. The results also indicate that it is challenging to modify this bias. Implications for research on attitude change, social cognition and PEB are discussed.