What is it about?
Vaccination decisions are not based only on the risk of infection or the personal costs of vaccination. People may also consider whether they could regret their choice, what others are doing, what others approve of, and how much they trust the available information. This study uses a computer simulation to explore how these influences interact during repeated epidemics. The results suggest that some flexibility in decision-making helps people learn from experience and adapt. Moderate regret can encourage people to reconsider poor choices, but excessive regret can make behaviour unstable. Similarly, some uncertainty may encourage caution, while too much uncertainty makes it harder for people to coordinate. Social norms can help when reliable information is limited. Personal beliefs matter more when people feel confident, while social approval and the behaviour of others become more influential under uncertainty. Overall, the study shows how emotions, uncertainty and social influence can work together to shape vaccination behaviour and epidemic outcomes.
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Why is it important?
What makes this study distinctive is that it brings together several influences on vaccination decisions that are usually studied separately: regret, uncertainty, learning, bounded rationality, and different types of social norms. The model distinguishes between personal beliefs, perceptions of what other people do, and perceptions of what other people approve of. It then examines how these factors change together as people learn from successive epidemic outbreaks. The work is timely because vaccine hesitancy and uncertainty about health information remain important public-health challenges. The findings show why the same message may not work equally well in every situation. For example, information about what others do can sometimes help but may also backfire, while messages about social approval may be more effective under uncertainty. By identifying when different behavioural influences support or undermine vaccination, the study can inform more carefully targeted communication strategies and contribute to better models of public responses during future epidemics.
Perspectives
I began this work from the view that vaccination decisions cannot be understood as simple calculations of costs and benefits. People also experience fear and regret, learn from previous outcomes, respond to social expectations, and often make choices with incomplete or uncertain information. I wanted to bring these elements together in a single model without losing sight of their psychological meaning. What I find most interesting is that none of these influences is simply beneficial or harmful. Some uncertainty can encourage caution, but too much can disrupt coordination. Regret can support learning, but it can also destabilize decisions when it becomes excessive. Social norms can promote vaccination, yet their effects depend on the type of norm and the wider context. For me, the study demonstrates the value of combining ideas from psychology, economics, epidemiology and complex-systems research to better understand real-world behaviour.
Christos Charalambous
University of Cyprus
Read the Original
This page is a summary of: Regret, uncertainty, and bounded rationality in norm-driven decisions, PLOS One, August 2026, PLOS,
DOI: 10.1371/journal.pone.0354748.
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