Johan Ugander

We are seeking a Fellow to lead cutting-edge research on short-form video content and its societal implications. Bridging the gap between computer vision, causal inference, and computational social science, the Fellow will focus on the large-scale analysis of TikTok data (using an existing, massive dataset). The position involves developing novel multimodal methods to understand how short-form algorithmic content shapes public opinion, political polarization, and online culture. This is a unique opportunity to work at the forefront of the field, combining rigorous social science research designs with state-of-the-art computational techniques.

The Center for Information Technology Policy at Princeton invites applications for a Postdoctoral Fellow to work with an interdisciplinary team (me, @bstewart.bsky.social, and @manoelhortaribeiro.bsky.social).

Link: puwebp.princeton.edu/AcadHire/app...

Please apply by THIS SUNDAY, Dec. 14!

I'm just saying one could, not that one should. Often there's a lot of things one shouldn't do… including community detection ;-)

Free idea: ever since I heard about Leiden and its popularity I wondered why nobody has modified it to use a connected CM null. I think people don't want to MCMC the null model edge probabilities. A lot of work! Tho I think often the graphs where people use Leiden aren't actually that large.

I'm sympathetic to your broader point, e.g., Leiden is overly self-congratulatory on its approach to connected community detection. But in defense of connectivity, the "switch chain" can sample from the connected configutation model null: theory.stanford.edu/~tomas/switc...

Ordrupgaard is another top notch art museum very close to Copenhagen! Different style focus. But world class for what it is.

Today, social media platforms hold the sole power to study the effects of feed-ranking algorithms. We developed a platform-independent method that reranks participants’ feeds in real time and used this method to conduct a preregistered 10-day field experiment with 1256 participants on X during the 2024 US presidential campaign. Our experiment used a large language model to rerank posts that expressed antidemocratic attitudes and partisan animosity (AAPA). Decreasing or increasing AAPA exposure shifted out-party partisan animosity by more than 2 points on a 100-point feeling thermometer, with no detectable differences across party lines, providing causal evidence that exposure to AAPA content alters affective polarization. This work establishes a method to study feed algorithms without requiring platform cooperation, enabling independent evaluation of ranking interventions in naturalistic settings.

New paper in Science:

In a platform-independent field experiment, we show that reranking content expressing antidemocratic attitudes and partisan animosity in social media feeds alters affective polarization.

🧵

Happy to announce the 2nd edition of our Summer School in Computational Social Science that will take place in the beautiful Villa del Grumello on Lake Como between June 22-26, 2026!

*** DEADLINE FOR APPLICATION: February 15, 2026 (firm deadline) ***

More details here:
css2.lakecomoschool.org

Community notes reduce engagement with and diffusion of false information online | PNAS Social networks scaffold the diffusion of information on social media. Much attention has been given to the spread of true vs. false content on onl...

Link to that paper: Slaughter, Peytavin, Ugander, Saveski (2025) "Community notes reduce engagement with and diffusion of false information online", PNAS. www.pnas.org/doi/10.1073/...

"Understanding the strengths and limitations of community-based responses to misinformation" — very nice commentary by @ekvraga.bsky.social in PNAS, covering my recent paper on causal effects of Community Notes w/ @isaacslaughter.bsky.social @axelp.bsky.social @msaveski.bsky.social

That MAGA Account Might Be a Troll From Pakistan How X blew up its own platform with a new location feature

I wrote about the fake account blowup on X this weekend. A genuine post-truth nightmare and proof that these companies have polluted their platforms so thoroughly and traded reality for profit that they've undermined the very idea of what the internet is supposed to be.

A Battle with My Blood When I was diagnosed with leukemia, my first thought was that this couldn’t be happening to me, to my family.

Powerful read. If you're a US resident age 18-35, consider registering for the National Marrow Donor Program (NMDP, formerly BeTheMatch): www.nmdp.org

Yale’s Institute for Foundations of Data Science (FDS) @yaledatascience.bsky.social is seeking applications for postdoctoral positions. These are cool, generously supported, competitive positions, expected to last 2-3 years, for independent scholars working on the foundations of data science.

📣 Postdocs at Yale FDS! 📣 Tremendous freedom to work on data science problems with faculty across campus, multi-year, great salary. Deadline 12/15. Spread the word! Application: academicjobsonline.org/ajo/jobs/31114 More about Yale FDS: fds.yale.edu

In economics we call these Manski Bounds.

New office trinket: I 3D-printed "Lewitt's missing cube". Quite happy with how it turned out. Many thanks to Paul for sending me the stl file! Skip to 49:55 in his video to appreciate why this is fun.

Excellent report on experiences of @guidoimbens.bsky.social & Mary Wootters co-teaching "Causality, Decision Making, and Data Science" to undergrads at Stanford fall 2024: hdsr.mitpress.mit.edu/pub/uynpjlow... Course material here: stanford-causal-inference-class.github.io

Does Claude do badges? Claude should do badges.

Artist Amy Sherald: The 60 Minutes Interview Amy Sherald spent years painting in obscurity, and almost died from a rare heart condition. Now 52, the artist behind Michelle Obama's official portrait is one of America's most celebrated painters.

ICYMI: Drop everything and spend 13 minutes with Amy Sherald--with her singular vision and talent, with her clarity about her central place in the jagged American story. You will be stirred by it all. www.cbsnews.com/video/amy-sh...

I had not seen that before, thanks for the pointer!

I don't agree that all these are examples where ethics let slip in a way "that wouldn't be acceptable for academics". Would love to chat in longer former about all this, best off social media :)

FWIW, I am deeply sympathetic to the thesis of the paper—for over a decade I have encouraged students interested in industry research to read Milosz's The Captive Mind in preparation. So I want to help you strengthen the work by encouraging precise arguments.

Huszár et al. wasn't an experiment, it was observational. And the UCSD and Cornell studies both went before IRB. So the journals didn't waive anything, as far as I know. I feel like precision here is quite important, because the history of these studies is full of muddled details.

Thanks, it just didn't seem like any of the three I knew the details of were "examples" of the previous sentence (journals waiving IRB).

Am confused…
- Bond et al [33] was approved by UCSD IRB.
- Thomas & Wahedi [39] both authors had only Meta affils; no university IRB had jurisdiction.
- Huszar et al [75] dunno, cc @inference.vc.
- Kramer at al [82] was exempted; much has been written about this case. See the PNAS ed statement.

Lake Wintergreen with fall foliage.

Lake Wintergreen with fall foliage.

Connecticut is approach peak fall. Shots from Lake Wintergreen this morning. A glorious start to the day.

Network Scientists with Karate Trophies The first scientist at any conference on networks who uses Zachary's karate club as an example may...

Cf. the Zachary Karate Club Club: networkkarate.tumblr.com cc @aaronclauset.bsky.social

New paper alert!!! 🚨

“A Short History of Misinformation-at-scale and Efforts to Mitigate it” in the Journal of Public Policy and Marketing

drive.google.com/file/d/1Klg9...

This article traces the social construction of misinformation-at-scale through changes to content moderation.

Have you ever wondered how to ensure a loss in Candyland though?

github.com/mkiang/candy...

Join the Social Algorithms Workshop at Yale to learn how algorithms amplify ideas, and (sometimes) mislead us, organized by @jugander.bsky.social w/ talks by @brendannyhan.bsky.social & @informor.bsky.social. Use code sawitonX on last registration page for 25% off yalefds.swoogo.com/socialalgori...

Re-upping for 2025.