Are Iowans Irrational to Fear Brain-Eating Amoebas? A Philosopher Weighs In

After a rare amoeba death in Iowa made headlines last summer, many open-water swimmers began questioning whether lakes were safe. But is that fear truly irrational, or is it an adaptive response to uncertainty? A philosopher argues the answer reveals deeper divides in how science and policy understand human decision-making.

The Iowa Connection: Rare Amoeba Death Sparks Fear

In July 2025, 12-year-old Jaysen Carr died after swimming in Lake Murray, South Carolina, from an infection caused by Naegleria fowleri, a rare amoeba found in warm fresh water. Each year, drowning causes roughly 4,500 deaths in the United States, while infections from brain-eating amoebas typically number only two or three. Yet the vividness of these rare deaths powerfully shapes how people perceive and respond to risk.

After a 2025 amoeba-related death made headlines in Iowa, open-water swimmers began questioning whether lakes were safe, even as health officials emphasized how rare such infections remain. This reaction raises a deeper question: What does it mean to call a response rational or irrational?

What Are the 'Rationality Wars' in Behavioral Policy?

Alejandro Hortal-Sánchez, a philosopher at Wake Forest University and the University of North Carolina at Greensboro, explores these questions in his research on behavioral public policy. He highlights a divide known as the rationality wars between behavioral economists like Daniel Kahneman and evolutionary psychologists like Gerd Gigerenzer.

Behavioral economists emphasize how heuristics, or mental shortcuts, produce systematic biases or predictable errors in judgment. From this perspective, these biases lead people to make choices that do not serve their own interests. Evolutionary psychologists instead see those same shortcuts as adaptive responses to uncertainty, efficient strategies shaped by the environments in which human reasoning evolved.

Why Nudges Work: Aligning Policy with Human Behavior

This perspective helps explain why small changes in choice environments, known as nudges, can significantly shift behavior without forcing anyone to choose differently. For example, framing the same medical procedure as having a 90% survival rate rather than a 10% mortality rate leads patients to respond very differently. Setting one option as the default, whether in organ donation, retirement savings, or privacy settings, leads most people to stick with it simply because opting out takes effort.

From a behavioral economics perspective, these are clear cases of bias. From an evolutionary perspective, relying on defaults or whatever feels most vivid can be an efficient way to decide without becoming overwhelmed. Nudges work precisely because they align with, not fight against, the shortcuts people already use, making the desired behavior the path of least resistance.

Should Policy Correct or Educate?

This divide reflects a deeper disagreement about human rationality itself. If human rationality is seen as deeply flawed, nudges appear attractive because they make better decisions easier without demanding reflection. If rationality is viewed as adaptive and teachable, policy should focus on strengthening people's capacity to learn, adapt, and decide for themselves.

Behavioral economists defend nudges as tools for correcting cognitive biases. Gigerenzer criticizes them as ethically problematic and argues that public policy should emphasize education over subtle choice manipulation.

Is Fear of Rare Amoebas Irrational?

Hortal-Sánchez argues that this apparent contradiction dissolves once you recognize that rationality is not a single thing. Human beings can be both rational and irrational, depending on the scientific lens in use. From a behavioral economics perspective, many decisions appear biased and suboptimal. From an ecological or evolutionary perspective, those same decisions can look adaptive, efficient, and sensible given the environments in which they are made.

Seen this way, fear of rare brain-eating amoebas, of flying, or of tap water is not simply a failure of reason. Such reactions may appear irrational under one standard yet reflect a form of rationality adapted to uncertainty, vivid impressions, and limited information.

What This Means for Iowa Policy and Everyday Life

For Iowans, this debate has practical implications. Whether the state government uses nudges to encourage retirement savings, healthy eating, or energy conservation, the underlying assumptions about human rationality shape those policies. If policymakers view people as deeply flawed decision-makers, they may favor subtle manipulation over education. If they view rationality as adaptive, they may focus on strengthening citizens' capacity to learn and decide for themselves.

Ultimately, what matters is not labeling people as rational or irrational, but being explicit about which conception of rationality is at work and why. That choice shapes whether public policy aims to nudge behavior, educate citizens, or redesign environments so that human reasoning can operate at its best.