Various decisions, such as installing surveillance cameras to deter thieves and enrolling in a smoking cessation program to reduce future health risks, are made to mitigate the risks encountered in daily life. Self-prevention or “self-protection” (*2) issues refer to situations wherein future risks are reduced through current investments. The traditional economic theory suggests that individuals with a prudent attitude (prudence) toward risks are proactive in terms of adopting preventive behavior. However, few empirical studies have examined the accuracy of this theory, known as the “expected utility model,” in explaining actual human behavior.

An economic experiment was conducted by Associate Professor Masuda and his colleague to analyze how individuals make decisions to mitigate risks. The participants were presented with a choice task using dice. The participants were permitted to roll the dice multiple times, and a reward ranging from a few hundred yen to a little over a thousand yen was awarded to them depending on their choice and the outcome of the dice roll. The “level of prudence” of the participants was measured based on their choice between an uncertain large reward and a certain small reward. The willingness of the participants to adopt preventive behavior, such as “how many surveillance cameras should be installed to prepare for the risk of burglary,” was examined based on the results. Notably, the findings of the experiment revealed a trend that was discordant with the traditional theory. In contrast to the expected finding, participants with a prudent attitude toward risks tended to exhibit reluctance in adopting preventive behavior. This finding indicates that human beings may not accurately perceive probabilities. For instance, the illusion of probability influences the adoption of preventive behavior, such as underestimating the effect of installing additional surveillance cameras.

Although our research thus far has focused on “individual preventive behavior,” in the future, its scope can be expanded to “group preventive behavior.” In particular, we aim to study decision-making mechanisms in situations wherein individual preventive behaviors have an effect on others, such as the prevention of infectious diseases and responses to the “free rider problem” (wherein individuals do not adopt preventive behavior and benefit from the preventive behavior of others). This study aimed to provide accurate insights into the characteristics of human behavior and contribute to designing social systems based on this understanding. Building a system that encourages the adoption of effective preventive behaviors and considers biases in risk perception will aid in solving various social issues in the future.