A research team led by Associate Professor Hiroshi Yamada of the University of Tsukuba has succeeded in constructing a theory that provides a unified explanation for the subjectivity of people who immediately feel that they are likely to hit another jackpot immediately after experiencing an unexpected jackpot.

 Human subjectivity is not perfectly rational, and the value of money can be subjectively distorted.For example, an increase of 100 yen from a state of 2 yen is more valuable than an increase of 1 yen from a state of having 2 million yen.Probability judgments can also be subjectively distorted.For example, even though the odds of winning the first prize in a lottery are extremely low, you might end up buying a lottery ticket just because you think you might win.Prospect theory universally explains human subjectivity regarding economic behavior.

 On the other hand, human subjectivity is not immutable, and from past reward experiences (whether the result was better or worse than expected), there is an aspect of learning behavior that is most profitable.Such changes in subjectivity are explained by a theory called reinforcement learning, which is completely different from prospect theory.

 In this research, we constructed a new "dynamic prospect theory" that integrates these two theories, and succeeded in explaining human judgment and behavior under uncertain circumstances in a unified manner.Analysis of behavioral data after repeated gambling experiments showed that, immediately after an unexpectedly large payoff, probability judgments were higher than predicted by prospect theory.Because dynamic prospect theory incorporates into prospect theory the property of reinforcement learning, in which subjectivity changes according to the degree of unexpectedness, it is said that this change in subjectivity based on gambling hits and losses can be explained well.In other words, the dynamic prospect theory can explain the subjective feeling that the more you experience a big win, the more likely you are to win the next one.

 Interestingly, essentially the same results were observed in similar experiments with macaque monkeys, which are closely related to humans.Based on this discovery, it is expected that studying the brains of monkeys will lead to an understanding of the mechanisms of the brain that create the various senses of money and probability that each of us has, as well as the joy of success. be.

Paper information:[Science Advances] Dynamic prospect theory: two core decision theories coexist in the gambling behavior of monkeys and humans

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