Laboratory for Social Minds

What is mathematics, how do we do it, and how will A.I. change it for ever? Thrilled to announce Explaining Universal Truths, a @templeton_fdn & @CMU_DietrichHSS project to fund an interdisciplinary team of philosophers, mathematicians, and cognitive scientists. We're hiring!🧵

I normally don’t respond to ad hominem attacks, but since @aarondymarskiy keeps repeating that I “seem to make a lot of basic mistakes when discussing behavioral genetics”, I thought useful to respond to his hit piece against me. For reference, here’s the context: - In December, I published a long piece detailing the methodological flaws of “Twins Reared Apart” studies (davidbessis.substack.com/p/twins-reared…) - Within days, Aaron published a weak rebuttal (hereticalinsights.substack.com/p/dizygotic-tw…) which I responded to. - Two month ago, he published an ad hominem piece against me, with title “David Bessis Does Not Know Much About Behavioral Genetics” (hereticalinsights.substack.com/p/david-bessis…) — I hadn’t replied to that one, but this is what I’m doing now. Aaron concedes that my Twins Reared Apart piece is “among the most successful posts on [Substack] on the topic of intelligence and behavioral genetics” — which is great — but he nevertheless thinks I’m making beginner’s mistakes. The trouble is that he’s hallucinating those mistakes. Example 1. “David Bessis keeps making is referring to correlations as percentages. He does this in his original article, as well as out loud in his interview on Econtalk. This is simply not done by those who know what they’re talking about in this field.” Wow, big deal🤣! Didn’t you know that 30% is the same exact number as 0.3? Sure, behavior geneticists usually write 0.3 rather than 30% when discussing heritabilities in scientific papers. But in popular books they often use percentages, because it speaks to the general public. And, in fact, heritability is commonly interpretated as “percentage of variance explained”. Eg, I’ve just checked Plomin’s “Blueprint” and, on page 9, he puts the heritability of intelligence at “50%”, so he’s also using percentages. By the way, Plomin puts at IQ heritability at 50%, not 74%, so he seems to be on the same side as me in not believing the ridiculously figures from “Twins Reared Apart” studies. Steven Pinker, on page 380 of “The Blank Slate”, writes “Genes 40-50 percent” — so he’s also using percentages, and he’s also putting the heritability of behavioral traits at around 40-50%. Example 2. “David Bessis Does Not Know How Heritability Is Calculated”, “ In four different instances, one could see him referring to the squared correlation (R2) when discussing heritability, as if that is part of the formula. In reality, heritability is only ever calculating using the base correlation (r). “ This one is crazy. Aaron accuses of making a mistake in a fomula that appears nowhere in my post. Yes, I’m using “R2” as a shorthand for “correlation” and Falconer’s formula uses R and not R^2. So what? Did I claim it used R^2? No, I didn’t. By the way, my notation does reveal one thing — that I’m a pure mathematician and not a behavior geneticist. But did I ever claim otherwise? To me, a linear regression is an orthogonal projection, and the correlation coefficient R is computed via the Pythagorean theorem. I thus view R as the square root of R^2. So, yes, I have an idiosyncratic geometry-inspired perspective on statistics — which is actually very useful when you do machine-learning. Do you seriously think Falconer’s formula is too complicated for me? In any case, I think that you will agree that when R^2 appears in a sentence like “both R^2 estimates were highly vulnerable to noise”, it has zero relevance whether it’s R or R^2. All instances at stake are of this sort. Example 3. ”David Bessis Does Not Know What My Argument Is. My response to his claims about the DZ data was very simple: analyzing their data tells us nothing, because the standard error is too high, and therefore the confidence intervals are too wide.” No, Aaron, we already discussed this — I understand your argument, I just think it is the worst possibly excuse for not publishing the DZ data. If the placebo group in your drug trial is too small and the standard error is too high, making your trial inconclusive, you can’t turn it into a conclusive trial by suppressing the data from the placebo group data and that the apparent effect on the treatment group is fully attributable to the drug. Finally, just for fun, this nugget: “David Bessis Is Being Groomed By Taleb and Gusev” I’ll let @SashaGusevPosts and @nntaleb comment on it, but I was under the impression that I wasn’t their style, and in any case I’m much too old for this stuff.

Teachers vs Professors This has been on my mind since I first encountered it almost 15 years ago. When I was in high school, I had a few teachers in the humanities/social sciences who were really, really good: deep, serious thinkers, with lots of interesting views synthesized over decades of globetrotting experiences. As teachers, even at a nice private school, they were not real “winners” in the sense of climbing a prestigious career ladder, and neither did they publish academic papers. You could call them very advanced amateurs, and as dabblers they got to toy with lots of interesting ideas, kind of randomly assembled, without outside judgment. When I got to the University of Chicago, known for its life of the mind in the humanities, I didn't really find anybody who seemed to be as deep or as interesting a thinker as these teachers I encountered in high school. I always wondered why. Partially, it's because I got lucky with my teachers. They were the best we had. Maybe I didn't get so lucky with my professors. But today I may have figured it out: I think the actual reason is that my professors at UChicago were, in a sense, winners on an academic career ladder. It’s an extremely competitive environment, and they had somehow made it to the top. By definition, this is a tremendously powerful filter. And I think this had actually filtered against a whole group of people whom I consider interesting. This has become especially clear over the last few years, as a lot of traditional academia has been losing prestige rapidly: people are trusting the kind of professorial expert class less and less and less. It turned out that professors of ethics and sociology are just as unethical and susceptible to groupthink as the general public. And the general conformity of ideology and thought in academia is now well-known. These professional humanities academics may publish papers that are respected or even highly esteemed within their own niche communities, but this particular value system has long since been removed from what I consider interesting, or, in many cases, even related to the pursuit of truth. Reflecting on it, the heart of the matter is that those teachers in high school were unconstrained by convention and had been allowed to fully lean into their interests — kind of like the platonic dream of academia — whereas the professors I encountered in university, even when very successful, had been conformed by the academia-industry pressure cooker and their work sanitized, professionalized, and ultimately made uninteresting under the constraints.

A few thoughts from talking to some of my favorite mathematicians (both for their work and, like, as people and friends) at the expMath meeting:

I've created a couple of mathematical games, both based on word problems in groups or semigroups. One of them could lead to a Polymath project if enough people are interested in it, as it is connected with an open problem. More details in a blog post linked below. 1/2

Holy See: People with Down syndrome have same sacred value. vaticannews.va/en/vatican-cit…

Your first meme was probably a Chuck Norris fact. Mine was. He died yesterday in Hawaii at 86, ten days after posting a video of himself throwing punches on his birthday. His caption: “I don’t age. I level up.” This is a little tribute. The real Chuck Norris was wilder than any meme about him. He lost his first three karate tournaments, then went 65-5 over the next decade. Six-time undefeated world middleweight karate champion. Black belts in five different disciplines. First person ever inducted into the Black Belt Hall of Fame, and the only martial artist to be named to it three separate times. His student Steve McQueen told him to try acting. That led to a fight scene opposite Bruce Lee in Way of the Dragon (1972), which became the highest-grossing film in Hong Kong that year. Then Walker, Texas Ranger ran 9 seasons on CBS, 194 episodes, broadcast in over 100 countries. But his biggest cultural moment started with a college freshman’s joke. In 2005, a Brown University student named Ian Spector built a random fact generator on the Something Awful forums. It was originally about Vin Diesel. When the novelty faded, Spector ran a poll with 12 celebrity options. Chuck Norris wasn’t on the list. He won anyway, by write-in landslide. By early 2006, the Chuck Norris Fact Generator was pulling 20 million pageviews a month. This was before Twitter existed, before Facebook was public, before YouTube had a single viral hit. A college kid’s joke website about a semi-retired action star became one of the most visited humor pages on the internet. It spawned six books (some hit the New York Times bestseller list), two video games, and a scene in The Expendables 2 where Sylvester Stallone’s character recites a Chuck Norris fact to Chuck Norris’s face. When asked about his favorite fact, Norris said it was: “They tried to carve Chuck Norris’ face into Mount Rushmore, but the granite wasn’t hard enough for his beard.” The meme ran for 21 years. Most memes last weeks. Chuck Norris Facts introduced more people to Chuck Norris than his movies ever did. For everyone born after 1995, he was never an aging action star or a karate champion. He was the guy who counted to infinity. Twice. The guy whose tears cure cancer, too bad he never cried. The last thing the internet saw from Chuck Norris was him throwing punches on his 86th birthday. Which is, honestly, the most Chuck Norris fact of all.

Chuck Norris, the martial arts champion who became an iconic action star and led the hit series “Walker, Texas Ranger,” has died. He was 86. Norris was hospitalized in Hawaii on Thursday, and his family posted a statement saying he had died Friday morning: It is with heavy hearts that our family shares the sudden passing of our beloved Chuck Norris yesterday morning. While we would like to keep the circumstances private, please know that he was surrounded by his family and was at peace. To the world, he was a martial artist, actor, and a symbol of strength. To us, he was a devoted husband, a loving father and grandfather, an incredible brother, and the heart of our family. He lived his life with faith, purpose, and an unwavering commitment to the people he loved. Through his work, discipline, and kindness, he inspired millions around the world and left a lasting impact on so many lives. While our hearts are broken, we are deeply grateful for the life he lived and for the unforgettable moments we were blessed to share with him. The love and support he received from fans around the world meant so much to him, and our family is truly thankful for it. To him, you were not just fans, you were his friends. We know many of you had heard about his recent hospitalization, and we are truly grateful for the prayers and support you sent his way. As we grieve this loss, we kindly ask for privacy for our family during this time. Thank you for loving him with us. variety.com/2026/film/news…

People have no idea of the conceptual density of every single symbol in this theorem (whose statement, full disclosure, I can't comprehend). This is typical of modern algebraic geometry. Never before had humans packaged that much cognitive load in seemingly innocuous letters.

I put the Declaration of Independence through the LinkedIn slop generator. Incredible.

Reminder that EVERYTHING is an achievement: St. Augustine was shocked to find St. Ambrose reading *silently* (reading was then social and aloud) and private silent reading only really took off 700 years after in the 12 century.

Attention is all we have: a conjectural theory of cognitive inequality — I never expected this to become the most-liked piece of my Substack, thank you everyone🥰! davidbessis.substack.com/p/attention-is…

🧵 1/14: Just days after Paul Ehrlich (the man whose 1968 book “The Population Bomb” predicted billions would starve) passed away, it’s the perfect moment to celebrate the scientist who proved Ehrlich and other doomsayers spectacularly wrong. Meet Norman Borlaug, the Iowa farm boy who launched the Green Revolution and quite literally saved a billion lives. This is the ultimate story of human ingenuity triumphing over scarcity.

"It is remarkable, and wildly counterintuitive, not only that the question "Who is in charge of the supply of bread to New York?" has no answer, but that the supply of bread to New York is better managed by a system in which there is no answer than by one in which there is." John Kay.

The central anxiety of professional class parenting is managing the dueling imperatives of providing a wholesome and supportive home for mental/emotional/spiritual health and exposing the brutally competitive reality of the standard they have to meet to avoid downward mobility

When I started talking with Leo 2+ years ago for "The Proof in the Code," he told me how he decided to build trust in Lean's kernel: keep it small enough that anyone could implement their own. It's like: if we all get the same answer to a complicated math problem, we can be confident that answer is correct. Pre-orders: quantabooks.org/books/the-proo…

Update: Jeremy’s essay is now on arXiv arxiv.org/abs/2603.03684 Simon DeDeo and Eamon Duede also wrote a brilliant paper “A Correspondence Problem for Mathematical Proofs” that, among other things, analyses why we formalise (referencing sphere packing) arxiv.org/pdf/2603.13680

Interesting dialect map and one theory as to why.

Every teacher I know personally is leaving the profession because students have become unteachable. They don’t read, they don’t talk to each other, they have no curiosity, no passion, no interest in learning. Giving kids unfettered access to screens has ruined a generation.

I proposed to Buzzard taking on complete FLT back in the fall after we did the Prime Number Theorem. He laughed me out of the room. After Sphere Packing, he's not laughing anymore.

Most people know Chris Sims as a giant of macro, but he also essentially founded the modern economics literature that takes the idea that people have limited attention seriously. This work put real structure on the idea that attention is scarce, and it has shaped a huge body of research across macroeconomics, finance, and behavioral economics, including much of my own work over the past decade. The standard benchmark in economics is that people process all payoff-relevant information; they attend to all features of the information environment and make decisions based on the relevant payoffs. Behavioral economists such as Herb Simon challenged this view with the idea of bounded rationality, but without a specific account on what limited attention would look like. Chris's paper on *rational* inattention changed all that by putting real structure on the problem. It was a pretty simple idea: People can't pay attention to everything, so they pay attention to features where neglect would be more costly. It turns out this very simple assumption generates profound implications for everything from finance and monetary economics, to health and insurance decisions. Behavioral economists (myself included) have followed this work by proposing models where attention is limited but not allocated rationally, e.g., salience-driven attention. When I gave a talk at Princeton two years ago on how salience-driven attention can lead to over/underreaction to information, Chris was in the front row asking questions and making comments that helped the paper tremendously. He will be missed.