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Could social media make us less polarized instead of more? We tested 5 algorithms on 3 platforms with 10,000 people for 6 months during the 2024 election, and found that the answer is yes. 🧵

We ran an international competition to design new social media algorithms, then used a browser extension to intercept users' feeds and re-ranked them in real time. Each algorithm could re-order, add, and/or delete posts and comments on Facebook, X/Twitter, and Reddit. 2/

The result: affective polarization dropped by an average of -0.03 SD (p<0.05), a 1.5 point shift on the 100-point feeling thermometer. By comparison, US polarization has risen ~0.6 points/year, so this is like reversing roughly 2.5 years of increase. 3/

Active time and engagements fell on Facebook and Reddit, but *increased* on X/Twitter. In any case the changes were small. Reducing polarization doesn't necessarily mean reducing engagement. Not every platform is on the frontier of good for society and good for business! 5/

The tradeoff: users reported slightly worse experiences (-0.04 SD) on the Neely Index. Maybe our research-grade algorithms were unpolished. Or maybe it's because seeing depolarizing content, like news, can be kind of a downer. This is an honest tension worth taking seriously. 6/

Unlike one-shot depolarization interventions, algorithm changes are structural. At 6 months we likely captured equilibrium effects, meaning sustainable results. And we couldn't measure network effects or change creator incentives, all of which would plausibly amplify results. 7/