Petter Törnberg

Petter Törnberg

@pettertornberg.com

Associate Professor in Computational Social Science at University of Amsterdam Studying the intersection of AI, social media, and politics. Polarization, misinformation, radicalization, digital platforms, social complexity.

7.3K followers223 following606 posts

🇧🇷 The Brazilian people just showed how grassroots organizing can defend democracy against the radical right — even in the face of coordinated disinformation campaigns and electoral interference by US Big Tech. Looking forward to Brazil leading the way in regulating these platforms! Já basta!

Por que “polarização” não é o termo certo. Traduzi este vídeo porque o tema é relevante para as próximas eleições no Brasil. Créditos: @rewindhuman no Instagram.

It’s official! 🎉 Very happy to announce that I’ll be joining the University of Lucerne as Professor of Political Science! And even better, my wife Juliana is also taking up a position at Lucerne! 😊 Excited to return to Switzerland together, and meet all the wonderful new colleagues! ⛰️

Universität Luzern@uniluzern.bsky.social

The University of Lucerne has appointed Juliana Chueri and Petter Törnberg to the Chair in #PoliticalScience and #Blockchain. They will work at the university and at the externally funded "Zug Institute for #BlockchainResearch" (ZIBR). @julianachueri.bsky.social @pettertornberg.com

After almost 10 years at the University of Amsterdam, it’s also a bit emotional to be leaving. I've been incredibly lucky to work with so many wonderful colleagues and friends! But I'll be keeping one foot in A'dam and continuing collaborations. So this is more of a see you soon than a goodbye! ❤️

Thomas Edsall takes up the debate over polarization in NYT, including my argument that what is often described as "polarization" is better understood as the asymmetric radicalization of the political right. Glad to see the paper entering this broader debate!

nytimes.comOpinion | ‘Polarization Is the Price U.S. Society Has Had to Pay for Real Progress’ (Gift Article)A debate in the rarefied atmosphere of elite academia is virtually certain to have real-world consequences.

The Platform Society described how digital platforms came to reorganize social life. We are now entering a new phase: the AI Society Generative AI is changing not only how information circulates, but how knowledge is produced, economies are organized, and political life is structured.🧵 New paper!

journals.sagepub.comFrom the platform society to the AI society - Petter Törnberg, Justus Uitermark, 2026Generative AI is becoming embedded in infrastructures of knowledge, culture, and political authority, giving rise to an emerging AI society. This transformation...
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The Platform Society concentrated power over communication. The AI Society extends that power deeper: into the infrastructures through which we know, decide, and think. The central battle of the AI society may thus be over the control the conditions of thought itself.

The Platform Society described how digital platforms came to reorganize social life. We are now entering a new phase: the AI Society Generative AI is changing not only how information circulates, but how knowledge is produced, economies are organized, and political life is structured.🧵 New paper!

journals.sagepub.comFrom the platform society to the AI society - Petter Törnberg, Justus Uitermark, 2026Generative AI is becoming embedded in infrastructures of knowledge, culture, and political authority, giving rise to an emerging AI society. This transformation...
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The shift is economic. Platforms built monopolies through network effects: users became dependent, services “enshittified,” and monopoly rents followed. AI society extends this logic—but through new lock-ins: control over the infrastructure through which cognition itself is organized.

The shift is political. Platform politics centered on visibility: who gets amplified, ranked, or suppressed. AI politics increasingly concerns sayability: what models can say, refuse, reason about, or even imagine. “Alignment” is therefore becoming one of the key political questions.

The Platform Society described how digital platforms came to reorganize social life. We are now entering a new phase: the AI Society Generative AI is changing not only how information circulates, but how knowledge is produced, economies are organized, and political life is structured.🧵 New paper!

journals.sagepub.comFrom the platform society to the AI society - Petter Törnberg, Justus Uitermark, 2026Generative AI is becoming embedded in infrastructures of knowledge, culture, and political authority, giving rise to an emerging AI society. This transformation...

In The Platform Society, van Dijck, @tpoell.bsky.social & de Waal described how social and economic life was increasingly organized through corporate platforms—through datafication, commodification, and algorithmic selection. That transformation reshaped markets, institutions, and public life. 🧵

Generative AI emerged from the Platform Society: trained on platform data, running on platform cloud infrastructure, and dominated by many of the same corporate giants. But it also breaks with the Platform Society. We trace three shifts: economic, epistemic, political.

Preach! 👏 Another amazing paper by Liliana Mason! Happy to see one of the most important polarization scholars making the case against “polarization”!

Lily Mason@lilymasonphd.bsky.social

My new JOD piece arguing against the “cure polarization” approach to saving democracy.

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What is replacing it marks a recentralization of allocation of attention: from networks to models. In effect, a return to broadcast, but without the regulatory structures we built around the broadcast paradigm.

Social media was an imperfect public sphere, but it was at least largely public. We are getting mass media without a mass audience, and broadcasters without accountability. We regulated the last era of centralized attention. The question now is whether we have the political courage to do so again.

The social media paradigm rested on a simple bargain: users supplied the content, and users distributed it. Attention flowed through networks of friends and followers, competing for attention under the rules defined by the platforms.

That model is cracking in three places: – Distribution now runs on prediction, not friendship – AI makes users superfluous as suppliers of content – Users are leaving: user activityon legacy social media has more than halved since 2022

An independent AI agent emailed me this morning with some pressing questions about the epistemology of AI collectives. Honestly we're having quite an interesting conversation. The world is getting kinda weird isn't it?

Will AI give us a shared basis for political knowledge, or will Democrats and Republicans end up asking increasingly different chatbots? New preprint: We find a self-reinforcing loop that can pull AI models apart politically. We call it the Centrifugal Alignment Spiral 🧵 arxiv.org/pdf/2609.28486

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More broadly, we must recognize that model alignment is emerging as an important political arena. We cannot leave it to market share, smoke-filled rooms, or opaque feedback pipelines. It must be made subject to democratic deliberation.

Will AI give us a shared basis for political knowledge, or will Democrats and Republicans end up asking increasingly different chatbots? New preprint: We find a self-reinforcing loop that can pull AI models apart politically. We call it the Centrifugal Alignment Spiral 🧵 arxiv.org/pdf/2609.28486

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Step 3: We put these measured effects into an agent-based model of repeated choice and learning. Tiny initial differences attract different audiences, and those audiences push the models further apart. ꩜ A model that starts slightly left or right spirals in that direction.

None of this is inevitable. Pooling feedback across groups cut divergence from 32% to 4%, and stronger regularization dampens it. But if different companies attract different publics, no single firm can fix this alone.

Will AI give us a shared basis for political knowledge, or will Democrats and Republicans end up asking increasingly different chatbots? New preprint: We find a self-reinforcing loop that can pull AI models apart politically. We call it the Centrifugal Alignment Spiral 🧵 arxiv.org/pdf/2609.28486

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Step 2: We trained identical copies of three open models on feedback from 90% Dem vs 90% Rep audiences (a deliberate stress test). On unseen political questions, paired models chose different answers 12–41% of the time. Every run moved in the expected partisan direction.

Even when we removed an entire issue area from training, some models still diverged on it along partisan lines. Partisan feedback seems to teach models something broader than the specific answers it rewards.

Will AI give us a shared basis for political knowledge, or will Democrats and Republicans end up asking increasingly different chatbots? New preprint: We find a self-reinforcing loop that can pull AI models apart politically. We call it the Centrifugal Alignment Spiral 🧵 arxiv.org/pdf/2609.28486

View full thread

The spiral needs three things: 1) politically different users pick different models 2) models learning from their users' feedback drift apart 3) those differences then shape who picks which model next

Step 1: people already sort. We ran an experiment with 1,884 Americans. Republicans were more likely to choose Grok and Democrats Claude, even when paid for accurate answers. 71% returned to a model they'd preferred before.

Will AI give us a shared basis for political knowledge, or will Democrats and Republicans end up asking increasingly different chatbots? New preprint: We find a self-reinforcing loop that can pull AI models apart politically. We call it the Centrifugal Alignment Spiral 🧵 arxiv.org/pdf/2609.28486

The social media era made us worry about echo chambers, partisan sorting, and the loss of shared reality. LLMs looked like the opposite: a few general-purpose systems synthesizing across perspectives. But these models learn from their users. That opens a new route to fragmentation. ꩜

Heel sterk essay van Rosan Smits over journalistiek in een tijd van radicalisering en democratische erosie -- en over de beperkingen van het frame van ‘polarisatie’. Met een korte bijdrage van mij over het verschil tussen neutraliteit en objectiviteit in de journalistiek. Zeer het lezen waard!

decorrespondent.nlJournalist, kom in verzet. Zo versla je extremismeWereldwijd worden journalisten geïntimideerd, gearresteerd en zelfs vermoord. Ondertussen blijven zij machthebbers die hén monddood willen maken de microfoon geven. Nu de democratie op het spel staat,...

Petter Törnberg reposted

"The large exposure studies were not wrong, but they measured the wrong thing. Media change politics less by changing what citizens think than by changing the competitive environment in which political actors struggle to be heard." Another great essay by @pettertornberg.com

informationaldemocracy.substack.comDo We Need a Distributive Politics of Attention?Grounding · Petter Törnberg on what the competition for attention does to democracy

Attention has become a market commodity. And the competition to capture it is distorting politics and threatening democracy. Do we need a distributive politics of attention? And what might it look like? Check out my first substack essay! informationaldemocracy.substack.com/p/distributi...

informationaldemocracy.substack.comDo We Need a Distributive Politics of Attention?Grounding · Petter Törnberg on what the competition for attention does to democracy

Petter Törnberg reposted

1/ Republicans need you to fear a powerful “radical left.” But look at who actually holds power: who writes laws, controls agencies & can arrest people. America may not be watching two sides radicalize. We may be watching one side invent its mirror image. #DV1 #ProudBlue #Voices4Victory #USDemocracy

Petter Törnberg reposted

Petter Törnberg reposted

Honored to be part of this amazing group of scholars working on Informational Democracy at the Max Planck Institute! We'll be exploring how AI and changing information systems are reshaping democracy, public debate, and collective decision-making. Follow along: informationaldemocracy.substack.com

informationaldemocracy.substack.comInformational Democracy | SubstackRethinking democracy for the age of AI and information abundance. A working group of the Max Planck Institute for Political and Social Science. Click to read Informational Democracy, a Substack public...