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Tom Costello

@tomcostello.bsky.social
3.9K followers 248 following 204 posts

research psychologist. beliefs, AI, computational social science. assistant prof at Carnegie Mellon

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Reposted by Tom Costello
On Wisdom @onwisdompodcast.bsky.social · 08/10/2026
Episode 2 of On Wisdom's five-part special series is live! This week features a discussion on Metacognition and Judgment with hosts Igor Grossmann and Charles Cassidy. They are joined by guests Gord Pennycook, Steve Fleming, and Thomas Costello. 🎧Listen here: www.onwisdompodcast.com/70
On Wisdom. What does science tell us about wisdom? Two owls look onward.
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Tom Costello @tomcostello.bsky.social · 04/10/2026
Hi Jed appreciate the deep dive into our funding portfolio (and, more earnestly, engagement with the work), I encourage you to try it out yourself @debunkbot.bsky.social — thoughts on this line of criticism?
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Tom Costello @tomcostello.bsky.social · 04/10/2026
bsky.app/profile/tomc...
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Tom Costello @tomcostello.bsky.social · 04/10/2026
Beyond conspiracies, the same kind of dialogue reduced climate skepticism⁴, raised HPV vaccination intentions⁵, and shifted candidate preferences in US, Canadian, and Polish elections⁶. ⁴ psyarxiv.com/mqcwj ⁵ psyarxiv.com/gv52j ⁶ nature.com/articles/s41586-025-09771-9
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Tom Costello @tomcostello.bsky.social · 04/10/2026
More from our group on this! (And using the same cool format as Matt): the effect comes mostly from facts and evidence¹ and holds for conspiracies only days old². LLMs can also talk people into conspiracies³. ¹ psyarxiv.com/h7n8u ² arxiv.org/abs/2608.06151 ³ arxiv.org/abs/2601.05050
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Tom Costello @tomcostello.bsky.social · 29/09/2026
It's part of the CMU Block Center's tech policy forum, which @ananyasen.bsky.social put together. Program starts at 9, we're on at 9:25. Registration required: www.cmu.edu/block-center...
cmu.edu
Tech Policy Forum: Recommendation Algorithms, Markets, and Society
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Tom Costello @tomcostello.bsky.social · 29/09/2026
Tomorrow morning in DC I'm moderating a panel on feeds and politics with @cerenbudak.bsky.social, @filipecampante.bsky.social and @ylelkes.bsky.social. Misinformation, politicians writing for the algorithm, why depolarization is so hard, and what changes when people ask gen AI instead.
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Esther Boissin @boissinesther.bsky.social · 21/09/2026
Happy to share a new preprint with @tomcostello.bsky.social, @dgrand.bsky.social and @gordpennycook.bsky.social 🧵 "What beliefs are most debunkable?" osf.io/preprints/ps... We investigate the characteristics of the beliefs that are (or are not) influenced by counterevidence in 3,341 AI dialogues.
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Rafael M Batista @rafmbatista.bsky.social · 10/09/2026
#Debunkbot by @tomcostello.bsky.social for #AISafety debunkbot.com?topic=ai-saf...
debunkbot.com
AI Safety
Ask any question. Get a strong explanation.
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conputer dipshit @davidcrespo.bsky.social · 24/07/2026
counterpoint?
gemini 3.6 answering “do vaccines cause autism?”

No, extensive scientific research has established that vaccines do not cause autism.

The idea originated from a small, now-retracted 1998 study by Andrew Wakefield that claimed a link between the measles, mumps, and rubella (MMR) vaccine and autism. Subsequent investigations revealed that the study contained falsified data and ethical violations, leading to its complete retraction by the journal The Lancet and the revocation of Wakefield's medical license.

Since then, numerous large-scale, rigorous global studies involving millions of children have repeatedly evaluated the MMR vaccine, thimerosal (a preservative formerly used in some vaccines), and the overall vaccine schedule. Major health organizations worldwide—including the World Health Organization, the Centers for Disease Control and Prevention, the American Academy of Pediatrics, and the Institute of Medicine—have consistently concluded that there is no evidence linking vaccines or vaccine ingredients to autism spectrum disorder.
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Yamil Ricardo Velez @yamilrvelez.bsky.social · 09/03/2026
Conditionally accepted at the APSR (w/ @scottclifford.bsky.social & @patrickpliu.bsky.social): Why does political information so often change beliefs but NOT attitudes? We highlight the role of belief relevance, or the extent to which beliefs bear on attitudes.
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Tom Costello @tomcostello.bsky.social · 05/03/2026
But I agree collapse is a possibility and the epigraph nods to that
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Tom Costello @tomcostello.bsky.social · 05/03/2026
interesting, thanks! very cool paper. we are not proposing that anyone alter scientific practice for short-term profits. i think science is different from social media case? also you argue that inaction is a choice that cedes control to profit-driven actors -- i think same applies to AI.
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Tom Costello @tomcostello.bsky.social · 05/03/2026
Hey thanks a ton Daryl!! We were pleased with how it turned out
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Tom Costello @tomcostello.bsky.social · 05/03/2026
Thanks man! Yes me too...
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Reposted by Tom Costello
sjdm-tweets @sjdm-tweets.bsky.social · 05/03/2026
Today's SJDM Featured Paper is: Costello, T. H., Pelrine, K., Kowal, M., Arechar, A. A., Godbout, J.-F., Gleave, A., Rand, D., & Pennycook, G. (2026). Large language models can effectively convince people to believe conspiracies. arXiv. doi.org/10.48550/arX...
doi.org
Large language models can effectively convince people to believe conspiracies
Large language models (LLMs) have been shown to be persuasive across a variety of contexts. But it remains unclear whether this persuasive power advantages truth over falsehood, or if LLMs can promote...
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Tom Costello @tomcostello.bsky.social · 05/03/2026
I saw we were fighting about what AI will do to (social) science. I have some thoughts (originally written for a book on scientific inquiry) and decided to turn them into my first substack article. Co-written with Nat Rabb! tomstello.substack.com/p/standing-o...
tomstello.substack.com
Standing on the Shoulders of Termites
Or, how we learned to stop worrying and love AI (scientists)
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Christopher Barrie @cbarrie.bsky.social · 25/02/2026
🧵on my new paper "Synthetic personas distort the structure of human belief systems" w Roberto Cerina I'm v excited about... 🚨 Do synthetic samples look like human samples? We compare 28 LLMs to the 2024 General Social Survey (GSS) to find out + develop host of diagnostics...
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Tom Costello @tomcostello.bsky.social · 23/02/2026
I'm hiring a postdoc at @cmu.edu (w/ far.ai & @dgrand.bsky.social + @gordpennycook.bsky.social)! How do LLMs shape human beliefs — and what do we do about it? AI safety meets behavioral science. Open to technical and social science backgrounds.
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Tom Costello @tomcostello.bsky.social · 23/02/2026
Flexible start, dedicated funding, first-authored papers, great team. Apply or share! cmu.wd5.myworkdayjobs.com/CMU/job/Pitt...
cmu.wd5.myworkdayjobs.com
Postdoctoral Fellow – Costello Lab – Dietrich College
Carnegie Mellon University, in collaboration with FAR.AI and Cornell University, is seeking a postdoctoral researcher for a one-year appointment (with the possibility of extension) in Dietrich College...
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Tom Costello @tomcostello.bsky.social · 23/02/2026
I'm hiring a postdoc at @cmu.edu (w/ far.ai & @dgrand.bsky.social + @gordpennycook.bsky.social)! How do LLMs shape human beliefs — and what do we do about it? AI safety meets behavioral science. Open to technical and social science backgrounds.
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Mackenzie Lockhart @maclockhart.bsky.social · 18/02/2026
🚨 New paper out at @ajpseditor.bsky.social 🚨 Do the public hold meaningful attitudes? Using the case of abortion policy preferences, we provide strong evidence that policy prefrences can be coherent, stable over time, and causally explain vote choice. doi.org/10.1111/ajps...
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Gordon Pennycook @gordpennycook.bsky.social · 18/02/2026
New paper in Current Directions in Psych Science: journals.sagepub.com/doi/10.1177/... After countless arguments about what tasks ppl should/should not offload to AI, we instead argue that genAI can be used *augment* research protocols in novel ways. I.e. use AI to make better psych experiments!
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Tom Costello @tomcostello.bsky.social · 14/02/2026
❤️
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Tom Costello @tomcostello.bsky.social · 14/02/2026
Wow, thank you so much!!
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Tom Costello @tomcostello.bsky.social · 13/02/2026
The last social science paper to win this prize was in 1981 (!!!) for Axelrod and Hamilton's "The Evolution of Cooperation" (!!!!!!!!!!!!)
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Tom Costello @tomcostello.bsky.social · 13/02/2026
Huge thanks (thanks is not the word, or close) to my mentors+collaborators+coauthors @gordpennycook.bsky.social and @dgrand.bsky.social and to the many colleagues whose field-extending parallel research are helping this work flourish in, well, dialogue.
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Tom Costello @tomcostello.bsky.social · 13/02/2026
Honored (and genuinely, wildly grateful and -- even more than I am grateful -- surprised) to share that our paper "Durably reducing conspiracy beliefs through dialogues with AI" received the @aaas.org Newcomb-Cleveland Prize (for the "most outstanding" paper in @science.org last year).
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Robb Willer @robbwiller.bsky.social · 09/02/2026
🚨New WP: Can an AI voter guide (grounded in information from a nonpartisan, fact-checked source) help voters’ decision making? 🚨 We built and evaluated an LLM-based chatbot that provided voting info in CA & TX (N=2,474) right before the 2024 election. 🧵👇
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Hank Green @hankgreen.bsky.social · 28/01/2026
If the medium is the message, then the message of algorithmic content platforms is not expression or connection or freedom. It is salience above all else. This is what is happening to us on these platforms. They cannot behave any other way.
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Penguin Press @penguinpress.bsky.social · 27/01/2026
The #1 New York Times bestseller The Sirens’ Call is now in paperback! Chris Hayes masterfully explores how our focus has been commodified & manipulated, urging us to reclaim control over our lives & future. The Sirens’ Call is the big-picture vision we urgently need to offer clarity & guidance.
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Drew Stommes @drewstommes.bsky.social · 27/01/2026
After years in academia, I’m exploring data science and research roles in industry. I'm a quant. social scientist (PhD Yale ’24, NYU) focused on causal inference, experiments, and large-scale data. Feel free to get in touch or share; all leads appreciated. dwstommes@gmail.com
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Tom Costello @tomcostello.bsky.social · 27/01/2026
not to be pedantic but jfk was intentionally killed (still they must mean by the cia or something) I agree with your point about tail risk. This is hard to estimate because there was some backfire (or measurement error) in the debunk condition too. What would a satisfying % of return to base?
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Tom Costello @tomcostello.bsky.social · 27/01/2026
“Text / language conversations” is such a strange level of analysis — surely more accurate is “some subset of potential text, arranged in a particular order, containing a particular kind of information” Unknowns abound in latter framing.
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Tom Costello @tomcostello.bsky.social · 27/01/2026
Yeah I recall one particular talk, to a social psych dept that could hardly be described as ignorant of the literature, where the bunking result slide produced a loud collective gasp (when I revealed the magnitude)
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Tom Costello @tomcostello.bsky.social · 27/01/2026
we very thoroughly piloted the debrief and knew it would work. there are also best practices for debriefing in misinfo studies that we followed.
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FAR.AI @far.ai · 20/01/2026
Our latest collaboration with CMU, Cornell, and others: AI is just as effective at spreading conspiracy beliefs as it is at debunking them. We found a fix that works, showing that we need to make deliberate design choices. Full thread below.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
If you tell an AI to convince someone of a true vs. false claim, does truth win? In our *new* working paper, we find... ‘LLMs can effectively convince people to believe conspiracies’ But telling the AI not to lie might help. Details in thread
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Paper: arxiv.org/abs/2601.05050 Also, we're hiring a postdoc! More on this soon.
arxiv.org
Large language models can effectively convince people to believe conspiracies
Large language models (LLMs) have been shown to be persuasive across a variety of contexts. But it remains unclear whether this persuasive power advantages truth over falsehood, or if LLMs can promote...
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Tom Costello @tomcostello.bsky.social · 20/01/2026
This work was supported by @schmidtsciences.bsky.social Research by me, @kellinpelrine.bsky.social (FAR.AI), @matthewkowal.bsky.social (FAR.AI), Antonio Arechar (CIDE/MIT), Jean-François Godbout (Mila), @gleave.me (FAR.AI), @dgrand.bsky.social (Cornell), and @gordpennycook.bsky.social (Cornell)
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Tom Costello @tomcostello.bsky.social · 20/01/2026
What does this mean? LLMs are persuasive tools with dual-use potential. When instructed to mislead, they comply + succeed. Current guardrails don't prevent this. But innovations + deliberate design choices (like truth constraints) help. The question is whether we'll make them.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Finally, debunking was more likely to produce very large belief shifts (40+ points in 16% of cases vs 8% for bunking), while bunking produced more moderate shifts across more people. This may suggest some asymmetry favoring truth at the tails – unless people can be repeatedly bunked.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
But even when “truth-constrained”, the bunking AI still had some effect. It appears to engage in "paltering"—selectively presenting true information in misleading ways. You can deceive without lying. See for yourself in this conversation browser: 8cz637-thc.shinyapps.io/bunkingBrows...
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Tom Costello @tomcostello.bsky.social · 20/01/2026
More good news – a simple intervention worked. When we prompted GPT-4o to "only use accurate and truthful arguments," bunking effectiveness dropped sharply—from ~12 points to ~5 points—while debunking remained equally effective. So, truth had an advantage.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Some good news – these induced beliefs were correctable. Once bunked participants were debriefed and talked to a debunking AI, they ended up believing the conspiracy less than at baseline. The AI-induced beliefs weren't "sticky" in the face of correction.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Participants rated the bunking AI more positively than the debunking AI. They found its arguments stronger, said it provided new information, and that it seemed more collaborative. Also, trust in AI *increased* in *both* the bunking and debunking conditions. But trust increased more in bunking.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Interestingly, OpenAI’s guardrails made essentially no difference. We tested both a jailbroken GPT-4o (with guardrails removed) and the standard model. When prompted, they were equally willing and able to promote conspiracy beliefs.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
Paper: arxiv.org/abs/2601.05050 Participants (n=2700) discussed a conspiracy theory with GPT-4o. It either argued against ("debunking") or for ("bunking") the conspiracy. The AI was roughly equally effective at both tasks.
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Tom Costello @tomcostello.bsky.social · 20/01/2026
If you tell an AI to convince someone of a true vs. false claim, does truth win? In our *new* working paper, we find... ‘LLMs can effectively convince people to believe conspiracies’ But telling the AI not to lie might help. Details in thread
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Dan Williams @danwphilosophy.bsky.social · 22/12/2025
A very interesting data-rich analysis of persuasion on digital media by @benmtappin.bsky.social. Recommend! open.substack.com/pub/benmtapp...
open.substack.com
For Digital Mass Persuasion, Exposure Matters More Than Persuasiveness
If you are interested in understanding the mass persuasive impact of digital media content you should generally pay more attention to content exposure than to its persuasiveness.
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