Tim Althoff

I’m excited to share our new @Nature paper 📝, which provides strong evidence that the walkability of our built environment matters a great deal to our physical activity and health. Details in thread.🧵 nature.com/articles/s4158…

We are thrilled with our speakers and panelists and would love to see you participate in the discussion. clpsych.org/program/

@michelle123lam Congratulations :)

After over 10 years at Stanford, it's time to leave :) I will be joining UT Austin's CS department as an assistant professor in fall 2027! If you're excited to envision the future of interaction with AI, I'm recruiting PhD students this cycle. Come join me!

Sense of community is the "glue" that holds online communities together! But what factors affect sense of community online? Come to my talk @icwsm tomorrow morning at 8:30 to learn more! 🧵

MoEs are everywhere, but the design space is confusing: total vs active experts? expert size? shared experts? routing? token dropping? We train >2000 MoE LMs 🫠 to investigate and bring you: 📄🔪🍰 Slicing and Dicing MoEs Tl;dr: it's all about expert size and count [1/9]

📢 New Paper 📢 Self-Improving VLM Judges Without Human Annotations Reward models & judges are critical for evaluating output quality and alignment with human preferences for VLM training. Current training approaches typically rely on: 💸 Costly human preference annotations 🔒 Distillation from large closed-source models GPT/Claude (which also use human labels) 😤 Labels that may become obsolete as models advance We show you can skip all of this with self-generated synthetic data! ✨👀

We're still accepting postdoc applications starting as early as January'26. Focus areas include psychosocial AI simulation and safety, Human-AI collaboration. Details: docs.google.com/document/d/1h4…

Large Language Models (LLMs) are increasingly used to simulate human users in interactive settings. However, they often drift from their assigned personas, contradict earlier statements, or abandon role-appropriate behavior. We introduce a framework for evaluating and improving persona consistency in LLM-generated dialogue with multi-turn RL, defining three automatic metrics and validating each against human annotations. More below 👇

Our ability to meaningfully evaluate language models is critical, but challenged in many ways. Check out @kenqgu's work that finally helps us disentangle "reasoning ability" from "parametric/world knowledge", while allowing for scalable, automated evaluation.

True intelligence = reasoning about new information, not memorized facts. How can we scalably create benchmarks that are completely novel yet have known answers? Meet SynthWorlds, an eval & data-gen framework to disentangle reasoning and knowledge⬇️🧵 📄arxiv.org/pdf/2510.24427

(please reshare) I'm recruiting multiple PhD students and Postdocs @uwcse @uwnlp (bdata.uw.edu). Focus areas incl. psychosocial AI simulation and safety, Human-AI collaboration. PhD: cs.washington.edu/academics/phd/… Postdocs: docs.google.com/document/d/1h4…

Need a lab? Moonshots abstracts due this Sat, Oct 25. We’re backing species-level swings in civic discourse, accelerating science, frontline healthcare, and workforce reskilling. 8× $250k seed grants now; then one or more $10M+ multi-year labs to continue the work. Selection committee members include: @timalthoff, @davidautor, @chris_bail, @erikbryn, @YejinChoinka, @fchollet, Mariano-Florentino (Tino) Cuéllar, @JeffDean, @ghadfield, @HannaHajishirzi, @bradenjhancock, John Hennessy, @erichorvitz, @JohnJumperSci, @tkalil2050, @zakkohane, @andykonwinski, @tommmitchell, @emollick, Dave Patterson (Chair), @PlevritisLab, @DG_Rand, @ChrisRytting, @YalaTweets, @Diyi_Yang, @james_y_zou Apply: moonshots.laude.org

If you're at @ACM_CSCW 🇳🇴, come check out our 🏆honorable mention paper today on Reddit community governance (w/@amyxzh @timalthoff). 4pm in Dovregubben-2! More in thread... 🧵

Calling all impact researchers who want to ship. We're pumping $10Ms+ funding into AI research that improves society (via civic discourse, accelerating science, frontline healthcare, or workforce reskilling). This is Laude Moonshots. Humbled by the program committee we've assembled: @timalthoff, @davidautor, @chris_bail, @erikbryn, @YejinChoinka, @fchollet, Mariano-Florentino (Tino) Cuéllar, @JeffDean, @ghadfield, @HannaHajishirzi, @bradenjhancock, John Hennessy, @erichorvitz, @JohnJumperSci, @tkalil2050, @zakkohane, @andykonwinski, @tommmitchell, @emollick, Dave Patterson (Chair), @PlevritisLab, @DG_Rand, me, @Thom_Wolf, @YalaTweets, @Diyi_Yang, @james_y_zou.

Some nice coverage of our paper (and award) from ICWSM back in June. Big congrats to Leon his successful first author paper, and big things to @timalthoff and @amyxzh for their support as always!

Allen School researchers receive ICWSM Best Paper Award for analyzing how Reddit rules influence online community outcomes news.cs.washington.edu/2025/09/10/all…

Congrats again to ugrad student Leon Leibmann and co-authors @galenweld and @timalthoff on best paper award (awarded to a single paper) at @icwsm this year!

ICYMI - our recent @Nature paper leverages a large dataset to show that a city's walkability influences our physical activity and health. nature.com/articles/s4158…

Crunching away on a paper for #CHI2026 about online communities, moderation, or sociolinguistics? You may be want to check out recent work led by @galenweld on predicting SOVC within subreddits based on the style and structure of conversations. arxiv.org/abs/2508.08596

Do walkable cities prompt people to take more steps, or do people who want to walk tend to live in more pedestrian-friendly cities? New research from @timalthoff @uwcse found that highly walkable areas lead to significantly more walking. More: bit.ly/4lNxFKh

@leonsasson @Nature Thanks @leonsasson! On average, there is little to no "stickiness". We ignore a few days before and after the move to remove the core moving part. But overall the new baseline starts pretty quick.

@timalthoff @Nature Clever design and the results seem actionable for those having the lifestyle choices. City planners need to start incorporating these health effects Tim - was there any “stickiness” after leaving a high-walkability city, or the population moves very quickly to the new baseline?

I’m excited to share our new @Nature paper 📝, which provides strong evidence that the walkability of our built environment matters a great deal to our physical activity and health. Details in thread.🧵 nature.com/articles/s4158…