Many think LLM-simulated participants can transform behavioral science. But social scientists lack accessible discussion of what it means to validate these models. Under what conditions can we trust LLMs to learn about human parameters? Our paper maps the validation landscape. 1/

I like this summary of CS’s shift toward empiricism, especially the bit on how the entrance of human concerns (privacy/HCI/etc), while obviously important, can entrench beliefs that the only way to understand is empirical (the bane of my existence for a few years, actually 🙂)

In a new blog post, I argue that CS is already an empirical discipline, even though we often act as if it is not (mostly to our students). https://t.co/gHSxaIJYzw

This paper shows that short-form video platforms (like TikTok) cause mobile usage to increase. Tiktok increases daily screen time by ~17% (28 mins) & shortens breaks between sessions by 20%. These apps reinforce habitual checking leading to more usage. https://t.co/tqsD4rV2IC

The Center for Information Technology Policy at Princeton invites applications for a Postdoctoral Fellow to work with Andy Guess (Politics/SPIA), Brandon Stewart (Sociology), and me (CS). https://t.co/U4lP6Ne8xe Please apply before Sunday, the 14th of December!

Sycophancy. Groupthink. Test-time Inverse Scaling. What if one unsupervised metric could detect all these reasoning failures? 🤯 🩵Presenting our NeurIPS'25: Martingale Score🩵 We propose a statistical test for "Belief Entrenchment" in LLMs - no labels required. Link to paper:

Working with Bob is amazing! And EPFL is a very exciting place to be!

📢📢 I'm looking for a postdoctoral fellow and so are many of my amazing faculty colleagues @PrincetonCITP. The center's mission is to understand and improve the relationship between tech and society. Apply soon for full consideration. Details: https://t.co/AGphhLkU60 The center

@gneubig Dang, those $50 come 1 yr too late! ;) For ICLR'24, we estimated 15% of AI reviews. Plus: papers w/ AI review have 5% (abs) higher acceptance chance---the "AI Review Lottery"... https://t.co/SS64YuG3Ue https://t.co/MevpVN8DS0 @manoelribeiro @VminVsky @im_td @russogiusep

This work was led by @amaarouf97! Who did a fantastic job over the summer (!) Cc: @KevTGreene @stfeuerriegel, and Jake Shapiro, whom I tried to find really hard on Twitter. It was also only made possible by this amazing initiative, which is the https://t.co/h1pt5r4Xtu!

Putting it together: Short-form video platforms act as a structural driver of mobile usage. They don’t just change what people watch; they change how much and how often they use their phones: longer total use, shorter breaks, more entrenched checking routines.

But is this about short-form video or about TikTok? We repeat the analysis in a later period when Instagram and Facebook also had short-form video. There, differences between TikTok adopters and others vanish—suggesting the effect is about the format, not the specific app.

When does this extra usage happen? Effects are concentrated during the day. We find no consistent evidence that short-form video increases nighttime mobile use beyond what other social media already does.

Who is most affected? Short-form video especially pulls in people who previously used their phones less: Low-intensity users: ≈31% increase in total mobile duration High-intensity users: ≈14% increase

Main finding: short-form video platforms meaningfully amplify mobile use. After adoption, total mobile duration increases by ≈17% (about +28 minutes/day for the average user), and the average time away from the phone (TAP) shrinks by ≈20% (about −29 minutes between sessions).

We use a matched, stacked DiD design: - Treatment: people who adopt TikTok - Control: people who adopt Instagram or Facebook in the same period Outcomes: - total daily mobile duration - number of sessions - average time away from phone (TAP)

We use passively collected, individual-level data from a large U.S. mobile panel (N=1,764), tracking every app and website people used on their phones. We focus on a period when TikTok offered short-form video and Instagram/Facebook did not! Short-form video was the key diff!

Short-form video raises concerns about compulsive use and well-being, but most evidence is correlational. We ask a simple question: What happens to people’s overall phone behavior when they start using a short-form video platform? Do they just swap one app for another?

TikTok and the likes transformed how we spend time on our phones. But do they increase mobile use, or just reshuffle what we already do? We find that adopting TikTok increases total mobile usage and shortens breaks from the phone. Preprint: https://t.co/KXfKXgJnXO

Congrats to the 10 computer science faculty members recognized for their outstanding teaching! 🎉 🏅 @ryan_p_adams 🏅 Zeev Dvir 🏅 @michaelfreedman 🏅 @praveshkkothari 🏅 @WyattLloyd 🏅 Alex Lombardi 🏅 @margmartonosi 🏅 @jonathanmayer 🏅 @manoelribeiro 🏅 David Walker