Thinking of Dieting? Think Game Theory
The Prisoner’s Dilemma is an interpretative framework for countless real-world scenarios. Jim Stone’s article “Willpower and Game Theory: Are you ready for the Prisoners Dilemma Diet” analyzes a struggle familiar to many Americans–dieting. He relates it to game theory by contextualizing dieting as a series of games; the strategies are either to defect and give into cravings or to cooperate and abstain; the players are the dieter’s present day and future selves.
The article links game theory with dieting and puts a unique spin on their relationship. Stone simplifies the countless eating decisions one makes while dieting to eating “donuts now” or “no donuts now”, paired with thinner and fatter selves in the future. There are four options and values is his model:
- A thinner self in the future + donuts now = 10
- A thinner self in the future + no donuts now = 7
- A fatter self in the future + donuts now = 3
- A fatter self in the future + no donuts now = 0
From this, it seems that the obvious answer to receive the greatest payoff is to enjoy donuts today and refrain in the future. What a perfect excuse to indulge, right? There’s a catch. The “other player” is the dieter’s future self who faces the same options; one’s future self also has incentive to defect and postpone the diet. If the player keeps defecting, he cannot ever reach a “thinner self in the future” and is actually left with options C and D, limiting the future him to a maximum value of 3. On the other hand, if present day self exercises self-restraint and opts to turn down the donuts now, he can receive the second best outcome of “thinner self in the future+no donuts now”. This rewards him with a value of seven. In addition, his future self can easily continue making the same healthy choice and have an average value of 7.
According to the payoffs and strategies Stone chose, the two equilibriums are to cooperate and continue cooperating or to defect and continue defecting in subsequent games. Once the game starts, it is easier to stick to the initial strategy because doing so offers the better payoff of the remaining options. In real life, however, the “game theory” for every American’s diet is different. The matrix depends on how much each individual values thinness relative to their ability to indulge in their favorite treats. The payoffs for each strategy will diverge from those Stone offered, thus explaining the wide gamut of lifestyle choices in the American population.
https://www.psychologytoday.com/blog/clear-organized-and-motivated/201404/willpower-and-game-theory