Individual adaptation to extreme heat and the interpretation of risk perceptions: Evidence from counterfactual beliefs

As climate change intensifies extreme heat, heat-health policies increasingly use alerts, forecasts, and behavioral guidance to encourage individual self-protection. Evaluations of such policies often track survey-based intermediate outcomes, including warning awareness, perceived heat risk or vulnerability, and protective behavior, in addition to health outcomes. Yet routine self-protection can make reported risk perceptions difficult to interpret: perceived risk may motivate prevention, while reported risk may already reflect the protection that respondents have adopted. In a web-based survey of residents of Tokyo's 23 wards, we elicit subjective probabilities of heatstroke under realized and counterfactual prevention scenarios. Respondents are randomly assigned to evaluate either a no-prevention scenario or a full-prevention scenario. Reported risk changes systematically with the assumed level of prevention, suggesting that reported risk perceptions may reflect both perceived susceptibility and behavior-conditioned reappraisal and may be misleading as stand-alone indicators in adaptation monitoring and evaluation. We also find that perceived risk under the no-prevention scenario is positively associated with realized preventive effort, suggesting that this counterfactual belief provides a more interpretable basis than realized-prevention risk for examining how perceived susceptibility relates to preventive effort.