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…

📢 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…

Huge thanks to my amazing co-authors @iamborisi, Abby King, Jennifer Hicks, Scott Delp, and @jure (representing @uwcse @Stanford @StanfordDeptMed @StanfordNMBL @Nvidia) 🙏

City planning is a powerful public health tool 🛠️. Investing in sidewalks, parks, and mixed-use zoning is a direct investment in citizens' health, making entire populations healthier. 💚