Po-Shen Loh: Mathematics, Math Olympiad, Combinatorics & Contact Tracing | Lex Fridman Podcast #183
Lex Fridman (host), Po-Shen Loh (guest), Narrator
In this episode of Lex Fridman Podcast, featuring Lex Fridman and Po-Shen Loh, Po-Shen Loh: Mathematics, Math Olympiad, Combinatorics & Contact Tracing | Lex Fridman Podcast #183 explores po-Shen Loh on math, invention, and rethinking pandemic control systems Lex Fridman and Po‑Shen Loh discuss how genuine mathematical thinking is about invention and reframing hard problems, not memorizing methods, and how Olympiad-style challenges build that skill. Po explains his teaching philosophy, live-problem-solving approach, and why middle school is a crucial moment to help students experience creating their own solutions. A major portion focuses on NOVID, his privacy-preserving, network-theory-based app that reframes contact tracing as early-warning risk information aligned with personal incentives and freedom. They also touch on combinatorics, distributed algorithms, voting systems, and the broader question of pursuing long-term, high-impact work whose ideas outlast one’s own lifetime.
Po-Shen Loh on math, invention, and rethinking pandemic control systems
Lex Fridman and Po‑Shen Loh discuss how genuine mathematical thinking is about invention and reframing hard problems, not memorizing methods, and how Olympiad-style challenges build that skill. Po explains his teaching philosophy, live-problem-solving approach, and why middle school is a crucial moment to help students experience creating their own solutions. A major portion focuses on NOVID, his privacy-preserving, network-theory-based app that reframes contact tracing as early-warning risk information aligned with personal incentives and freedom. They also touch on combinatorics, distributed algorithms, voting systems, and the broader question of pursuing long-term, high-impact work whose ideas outlast one’s own lifetime.
Key Takeaways
Teach math as guided invention, not method rehearsal.
Po argues students should regularly face problems they initially *can’t* do, with hints and dialogue that help them invent methods themselves; this builds a durable skill of creating solutions rather than memorizing procedures they’ll soon forget.
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Use positive incentives in epidemic tech by serving self-interest.
NOVID doesn’t just tell you after exposure to quarantine for others’ benefit; it tells you how many ‘hops’ away active cases are in your physical contact network, so your selfish desire to avoid illness naturally drives adoption and cautious behavior.
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Respect privacy by modeling *relationships*, not locations.
Instead of GPS, NOVID uses Bluetooth-based proximity snapshots over time to infer strong, recurring contacts, allowing effective network-based risk estimation while avoiding precise geolocation and preserving anonymity.
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Think in terms of feedback loops and control, not just rules.
Po frames pandemic policy as a control-theory problem: classical contact tracing fights human incentives (removing people ‘against their will’), whereas informing people of approaching risk creates a feedback loop where individuals voluntarily reduce contacts.
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Competitions can be training grounds for general problem-solving.
Math and programming contests, when focused on deep problems and efficient algorithms, train skills—like reframing, abstraction, and back-of-the-envelope complexity analysis—that transfer directly to startups, research, and real-world systems design.
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Measure educational success by long-term impact, not short-term wins.
As IMO coach, Po cares less about medal counts and more about how many students later show up in the New York Times for big contributions; he designs training to cultivate future innovators, not just contest champions.
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Aim for hard, high-upside ‘campaigns’ rather than comfortable goals.
Borrowing from wartime and fantasy ‘campaign’ narratives, Po suggests choosing problems that would truly matter if solved—like better disease control—even if they require years of effort and may fail, because the bigger regret is not attempting them.
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Notable Quotes
“I don’t want to ever just tell somebody, ‘Here’s how you do something.’ I prefer to say, ‘Here’s an interesting question… do you have any ideas?’”
— Po‑Shen Loh
“We changed the paradigm from ‘what already happened, quick damage control’ to ‘predict the future.’”
— Po‑Shen Loh
“Free market capitalism was not based on altruism. If you set up the incentives so that everyone maximizing their own situation helps the whole, that’s a game-theoretic solution.”
— Po‑Shen Loh
“If you solve any one of the six problems at the IMO, you’re a genius.”
— Po‑Shen Loh
“I wanted to maximize how many person‑years after I’m gone what I did still matters.”
— Po‑Shen Loh
Questions Answered in This Episode
How could NOVID’s network-distance concept be integrated into official public health infrastructure without compromising its decentralization and privacy guarantees?
Lex Fridman and Po‑Shen Loh discuss how genuine mathematical thinking is about invention and reframing hard problems, not memorizing methods, and how Olympiad-style challenges build that skill. ...
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What concrete classroom practices can ordinary teachers adopt to shift from ‘show and drill’ toward Po’s improv-style, student-driven proof discovery?
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To what extent can current AI systems realistically tackle Olympiad-style problems that require multi-step, non-obvious insights rather than pattern-matching?
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How might the voting-tree and network ideas discussed be applied to design fairer, more robust real-world electoral systems or governance structures?
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For someone who abandoned math after school, what’s an actionable, sustainable way to reintroduce problem-solving into daily life without it feeling like test prep?
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Transcript Preview
The following is a conversation with Po-Shen Loh, a professor of mathematics at Carnegie Mellon University, national coach of the USA International Math Olympiad Team, and founder of Expi that does online education of basic math and science. He's also the founder of Novid, an app that takes a really interesting approach to contact tracing, making sure you stay completely anonymous, and it gives you statistical information about COVID cases in your physical network of interactions so you can maintain privacy, very important, and make informed decisions. In my opinion, we desperately needed solutions like this in early 2020, and unfortunately, I think, we will again need it for the next pandemic. To me, solutions that require large-scale distributed coordination of human beings need ideas that emphasize freedom and knowledge. Quick mention of our sponsors: Jordan Harbinger Show, Onnit, BetterHelp, Eight Sleep, and LMNT. Check them out in the description to support this podcast. As a side note, let me say that Po and I filmed a few short videos about simple, beautiful math concepts that I will release soon. It was really fun. I really enjoyed Po sharing his passion for math with me in those videos. I'm hoping to do a few more short videos in the coming months that are educational in nature on AI, robotics, math, science, philosophy, or if all else fails, just fun snippets into my life on music, books, martial arts, and other random things if that's of interest to anyone at all. This is the Lex Fridman Podcast, and here's my conversation with Po-Shen Loh. You know, you mentioned you really enjoy flying and experiencing different people and different places. There's something about flying for me, I don't know if you have the same experience, that every time I get on an airplane, it's incredible to me that human beings have actually been able to achieve this. (laughs) And, and when I look at, like, um, what's happening now with humans traveling out into space, I see it as all the same thing. It's incredible that humans are able to get into a box and fly in the air, and, and safely, and land. And the same, it seems like, and everybody's taking it for granted, so when I observe them. It's, it's quite fascinating because I s- see that cleanly mapping to the world where we're now on, on, uh, in rockets and traveling to the moon, traveling to Mars. And at the same kind of way, I can already see the future wh- where, where we will all take it for granted. (laughs) So I don't know, I don't know if you have, uh, you personally when you fly have the same kind of magical experience of like, how the heck did humans actually accomplish this?
So I do, especially when there's turbulence-
(laughs)
... which is, you know, like on the way here-
Yeah.
... uh, there was turbulence and it, the, the plane jiggled. Even the flight attendant had to hold onto the side.
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