In a scene that could easily have been featured in an episode of an American television sitcom, The Big Bang Theory, the late American physicist Richard Feynman once visited a Thai restaurant he frequented with a mathematical puzzle: How brave should we be in trying new dishes? Feynman quickly solved the puzzle on a single sheet of paper.

Now, behavioural scientists have revisited Feynman’s solutions – some of which his illegible handwriting obscured – and found that he really had the best strategy.

Feynman’s dilemma is one that any restaurant goer will be familiar with. Do we keep ordering the best dish we’ve ever had, or do we browse the menu hoping to find something better? A study published in Proceedings of the National Academy of Sciences on June 1 investigates this question and includes empirical findings that participants adopt food choice strategies that closely approximate Feynman’s mathematical solution.

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Shoham Choshen Hillel, a behavioural scientist at the Hebrew University of Jerusalem, says the authors have written a “super-creative article”. “The restaurant example stands for decisions in many settings,” she adds. Real-life examples include choosing a house to buy, deciding who to partner with, and choosing a parking space.

Are you ready to order?

The story begins with a regular visit. Feynman, a Nobel Prize-winning physicist at the California Institute of Technology in Pasadena, and his friend Ralph Leighton were at a Thai restaurant in nearby Glendale in the late 1970s. (Leighton helped Feynman write his famous 1985 memoir. Of course you’re kidding, Mr Feynman! and was the son of the late physicist Robert Layton, co-author of the influential 1964 Feynman’s Lectures on Physics, along with Feynman and Matthew Sands.) Leighton wondered whether he should order the ginger chicken—his favourite dish—or explore the rest of the menu. Feynman began writing and immediately claimed that he had found a mathematical solution: in his simplified model of the situation, he calculated a limit—over several rounds, Leighton’s rational decision would always be to settle on his favourite dish.

What Feynman did was turn the restaurant dilemma into a question in decision theory—a field at the intersection of economics and psychology that analyses strategies in a person’s game. In particular, it was an original contribution to a large family of problems in decision theory known as stopping problems. These include real-life problems in which one has to decide whether the prospect before him is good enough or whether to continue searching.

Leighton saved the notes, and years later partially copied Feynman’s spidery cursive as well as he could. Layton explained his interpretation in an article posted online in the early 2000s. A decade later, in 2013, Tom Griffiths, a cognitive scientist at Princeton University in New Jersey, became interested in the question while researching a book with his colleague Brian Christian, a computer scientist and cognitive scientist. Then Griffiths copied Feynman’s notes in full for the first time.

Christian, now at the University of California, Berkeley, says the question lay dormant for about another decade, until two researchers decided to revisit it in 2021. “We understood the meaning of Feynman’s notes, but we still had all the work to do,” he says. The researchers then went on to confirm that Feynman had indeed found the optimal solution and also solved a general version of the problem.

Behaviour matches maths.

Together with a third co-author, cognitive psychologist Evan Rasek at the City University of New York, the team decided to test whether people’s choices resembled something close to a mathematical solution. They translated the restaurant question into an online game, recruiting 2,520 participants to answer it. Participants were instructed to imagine visiting a new city for between one and four weeks and to choose which restaurant to dine at each night. Players could earn points based on the quality of their chosen restaurant (a number between 1 and 100) and were told to try to maximise their total points. Participants became less willing to take the risk of trying new restaurants as the end of their visit approached, which followed a logic similar to Feynman’s optimal formula.

Although the participants didn’t work on the math solution—which involves a formula with square roots—their behaviour was very close to it.

Choshen-Hillel says, “The fact is, even in this simplified setting, they still observe that people behave in fairly uniform—and fairly efficient—ways.”

Choshen-Hillel says that while Feynman’s problem can be used in economics and marketing, it doesn’t fully capture how people behave in a restaurant. Notably, Christian says, the model doesn’t account for boredom, since players’ best option is to settle on the same dish for a long time. In real life, one might want to choose the same dish every other time, say, and continue exploring the menu on other visits. But the problem boils down to “this basic tension that’s so familiar every day: the decision between doing what you love and trying something new”, he says.

This article has been reproduced with permission. This article was first published on June 1, 2026.

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