Researchers from the University of Tsukuba have developed a model called “dynamic prospect theory” that combines prospect theory and reinforcement learning theory. This model explains decision-making under uncertainty and accurately describes the choices made by humans and monkeys in gambling experiments. The study found that both humans and monkeys tend to behave as if they believe they are more likely to win again after unexpected wins. The researchers observed that this change in behavior is driven by a shift in the perception of probabilities rather than the valuation of rewards. The study suggests that investigating the monkey brain can provide insights into the brain mechanisms involved in risky decision-making and the perception of rewards.