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Felix Lennert @felixlennert.bsky.social · 10/03/2026

It gives me tremendous pleasure to announce that I managed to defend my Ph.D. thesis at ENSAE, IP Paris, last week. I forgot to take the customary pictures with my committee, so please enjoy the acknowledgments. You can find a summary of the thesis in French and English as well.

Acknowledgments
Note: I’ve listed people in alphabetical order and groups in roughly chronological order. The former serves to avoid inter-personal conflict,
the latter to avoid inter-group conflict.
As a sociologist, I will happily admit that this thesis is less of a personal achievement but rather the
result of being surrounded by excellent people. This section is dedicated to them.
Stepping onto the aesthetically challenged campus of the University of Regensburg after a turbulent
high school career felt like a breath of fresh air. I cannot thank Melanie Walter-Rogg enough for the life-
altering introduction to empirical research methods, the excellent mentorship, and the trust she put in me
when letting me off the leash to teach students for the first time.
My 5 years there would not have been the same pleasant experience without my community of avid
library users. Benedikt, David, Felix, Janik, Ludwig, Martin, Patrick, Sebastian, Stefan, Tarek, Tilman, and
Tobias, you changed my perspective on course work from it being a mere chore to rather being a side
effect of a nice day with friends. Thank you.
Linköping University came with a nicer view and the perfect fit in terms of program. The Master’s
program in Computational Social Science provided me with excellent education and I found myself, again,
surrounded by great people. The motley crew at the Institute for Analytical Sociology taught me to think
out of the box and then back it up with rigorous analyses. A special thanks goes to Marc Keuschnigg for
taking me on as his mentee, and eventually Research Assistant, for providing perspective when required,
and challenging my thinking whenever needed. This thesis would not have been written if it had not been
for your example of how interesting and fulfilling research as a profession can be.
Norrköping also provided a temporary home to a great group of people. Adedapo, Gustav, Jan, Pablo,

Paul, and Simona, thank you for making the dreary Swedish winter more bearable and the darker days
brighter.
My academic journey would have ended there, had it not been for Étienne Ollion. He trusted my
abilities and extended them in unforeseeable ways in Paris. Thank you for introducing me to a whole
new level of rigor, teaching me invaluable soft skills, and giving me the room and possibilities to thrive.
I thoroughly enjoyed our collaboration, be it the Summer Institute in Computational Social Science, the
NLP & Society seminar, or the countless hours that we spent working through my scattered ideas and
sub-par writing. It is only now in hindsight that I come to slowly appreciate how your mentorship has
formed my thinking and the way I navigate the world.
My time at CREST would have not been the same without my colleagues there. Thank you, especially,
Felix, Luis, and Sofian, for helping me navigate the particularities of life in France and making me feel less
alienated in the big city. Annina, Arnout, Emma, Germain, Jeanne, Julia, Mathis, Matteo, Maxime, Patrick,
Pedro, Théo, Vincent, and Yasmine, I hold our time in high esteem and am grateful that we essentially
never discussed work but rather focused on the fun parts of life.
I also need to thank Emiliano Grossman and Samuel Coavoux for serving on my Comité de Suivi. You
made these meetings never feel like the chore that they can be but rather a productive check-in that helped
steer the projects in a more productive direction.
Finally, Frédéric Gonthier for his thorough engagement with this manuscript and for serving as the
Président on my committee.
I also had the opportunity to visit Duke University twice. This is all thanks to Professor Stephen Vaisey.
Thank you for taking me on as a Visiting Scholar, for your great hospitality, and for providing an excellent
environment for intellectual growth. The Worldview Lab is a unique place and I will always think of my
stays there very fondly.
This is especially cou…

Julius, Leonie, Sascha, and Stephan for making these days feel shorter and (sometimes) the nights a bit
longer. I also thank my students for being such a great audience for my ramblings on text as data, I hope
you could learn something.
A heartfelt thanks goes to my co-authors for bearing with me when I switched analysis plans around,
and for keeping me in check with writing and analysis schedules. Alexi, Anastasia, Elida, Maans, Miriam,
Patrick, and Väinö, thank you very much for genuinely fun and inspiring meetings and great conference
visits.
Furthermore, there are people outside the ivory tower that academia can be that have made this jour-
ney easier. A special thanks goes out to Sven for showing me life outside the academy, for repeated hosting
in Los Angeles when I was craving Vitamin D, and weekly calls during what can definitely be considered
the loneliest time of my life. In addition, I thank Jan, Johannes, Lars, Selden, and Tim for the excellent bike
packing trips against the backdrop of the most magnificent sceneries. Thank you, Steven, for being an En-
glish speaker in a French environment and for exploring the beauties of the French back country together.
Thank you to the folks at home for making my stays back there like actual vacations and grounding me.
I’m unsure if I could have made it through the final stretch without the unwavering support of the
world’s kindest person, most-loving cat mom, my best friend, partner, intellectual inspiration, and wife,
Alexandra. Thank you for your 5 A.M. wake-up calls and your kind – yet rigorous – feedback on my
meandering sentences. I cannot wait to come home to Boston, the cats, and you now that this ordeal
is over. Thank you also to my new American family, Lawrence, Nora, and Ritchie, for your support in
transitionary times, excellent hosting, and great feedback on my English.
Finally, I need to extend my special gratitude to my family. My parents for the unconditional support
in all my endeavors, my brothers …

Abstract: This dissertation investigates three
facets of political polarization – ideological, affec-
tive, and lifestyle – in European multi-party democ-
racies. While extant research has overwhelmingly
focused on the United States’ two-party system, this
serves as a test for the generalizability of polariza-
tion theory across party systems. The first chap-
ter, combining 25 years of French survey and news-
paper data, demonstrates that media reflect opin-
ion division on established issues while elite cues
shape emerging issue alignments. The second chap-
ter, using bi-weekly survey data and automated
classification of social media messages during Ger-
many’s 2021 elections, shows that polarized elite
rhetoric directly predicts mass affective polarization
in real-time, with effects moderated by strength of
party identification. The third chapter, examining
Swedish Twitter users’ following behavior, extends
lifestyle polarization theory to multi-party systems,
revealing that “cultural bundles” of everyday inter-
ests align with broader ideological blocs rather than
specific parties. Across these chapters, I demon-
strate how digital traces of human behavior com-
bined with representative survey data can capture
and advance polarization theory in naturalistic set-
tings.

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Felix Lennert @felixlennert.bsky.social · 09/08/2025

Studying a social science will really change how you walk the earth and see society Me, after 11 years of studies: LOL, Coleman cooler, just like the boat/bathtub

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Étienne Ollion @eollion.bsky.social · 23/06/2025

SICSS-Paris is on! Today, over 40 scholars from all over Europe (and beyond) gathered at @crestumr.bsky.social for 2 weeks of courses and talks about digital methods and text analysis. And in the evening, @eunjikim.bsky.social gave the first talk on influencers and political change.

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CREST Sociology @crestsociology.bsky.social · 19/06/2025

Next week, CREST is hosting another edition of the Summer School in Computational Social Science (SICSS). Check out the speakers and participants here: sicss.io/2025/paris/p... and some here: @bartbonikowski.bsky.social @eunjikim.bsky.social @austin-van-loon.bsky.social @dirkhovy.bsky.social

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Felix Lennert @felixlennert.bsky.social · 13/04/2025

Thank you for coming out and vibing with us and our poster at PAA. The poster session is over now. So if you haven’t stopped by, please feel guilty. Download the preprint and all your sins shall be forgiven (doi.org/10.31235/osf...)

One academic and one imposter (left) at an academic conference standing in front of their poster

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International Conference on Computational Social Science @ic2s2.bsky.social · 04/04/2025

Sarah Williams, Associate Professor of Technology and Urban Planning at MIT, will be a keynote speaker for #IC2S2 2025 in Norrköping, Sweden. 🎙Urban policy and big data for public good. Learn more: www.ic2s2-2025.org/keynotes/

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Marc Keuschnigg @marckeuschnigg.bsky.social · 25/02/2025

IC2S2 2025: As many of you have seen, the submission system was temporarily down. It is running again and we extended the deadline to include Feb 26. Please excuse the inconvenience

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Étienne Ollion @eollion.bsky.social · 24/02/2025

Among other great locations, Paris will also hold a Summer Institute. This year's focus will be on LLMs and GenAI. Join us!

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International Conference on Computational Social Science @ic2s2.bsky.social · 31/01/2025

Prof. Arnout Van de Rijt of Sociology at the European University Institute will be a keynote speaker for #IC2S2 2025 in Norrköping, Sweden. 🎙The long-term effects of good and bad luck on life course achievement. Learn more: ic2s2-2025.org. Stay tuned for more updates!

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Statistical Horizons @stathorizons.bsky.social · 03/02/2025

Interested in a free seminar? To mark our first semester on Bluesky, we’re offering a free seminar from our Spring offerings (through May 31) to one lucky winner. Follow us and repost this message by Monday, February 10 to enter. Winner revealed on Feb. 14—may the odds be in your favor!

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International Conference on Computational Social Science @ic2s2.bsky.social · 22/01/2025

IC2S2 2025 has received 23 tutorial proposals—thank you for your excellent proposals! Our review team is at work, and we look forward to announcing the lineup soon. Stay tuned: www.ic2s2-2025.org

ic2s2-2025.org

IC2S2'25 Norrköping

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International Conference on Computational Social Science @ic2s2.bsky.social · 13/12/2024

🚨 #IC2S2’25 Call for Tutorials deadline is just around the corner—Jan 17, 2025 Don’t miss your chance to shape the computational social science conversation in Norrköping, Sweden. Submit your tutorial proposal now: www.ic2s2-2025.org/submit-tutorial Keynote announcements are coming soon!

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CREST Sociology @crestsociology.bsky.social · 14/01/2025

NEW WORKING PAPER: CREST's @felixlennert.bsky.social and @ppraeg.bsky.social conduct a machine-learning text analysis of intergenerational mobility perceptions in Germany, Sweden, and the United Kingdom Now on @socarxiv.bsky.social: doi.org/10.31235/osf...

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Felix Lennert @felixlennert.bsky.social · 14/01/2025

I pressed some buttons on my keyboard, had a couple of meetings with Alexi Gugushvili and @ppraeg.bsky.social, and this came out: osf.io/preprints/so... Will probably write a more extensive description of this once I have wrapped up the teaching of this semester and reorganized my life.

osf.io

OSF

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Felix Lennert @felixlennert.bsky.social · 26/11/2024

Are you a nerd (like me) and want to shorten your loved one's/ones' wait until Christmas? Two unacknowledged AI helpers and I (the triumvirate of code taming) teamed up to program a little Shiny Advent calendar.

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Felix Lennert @felixlennert.bsky.social · 15/01/2024

Dear all, coming Wednesday, 17/1, at 17.15, we will welcome Alex Kindel (Sciences Po médialab) to our NLP & social sciences seminar. He will talk about his recent work on word embedding association tests. You can follow online. Find more information here: www.css.cnrs.fr/nlp-social-s...

css.cnrs.fr

NLP & Social Sciences Seminar 2023 – Program – CSS @ IPP

Site web de l'axe sciences sociales computationnelles du CREST-CNRS. Cours et tutoriels pour l'analyse des données numériques en sciences sociales.

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Felix Lennert @felixlennert.bsky.social · 07/01/2024

Spent a day recording videos for my "Toolbox CSS" course. All this stuff is online, so if you want to be taught web scraping and text mining by a 27-year-old with a Trainspotting haircut and a weird accent who religiously adheres to the tidyverse style guide, I've got you covered: bit.ly/tool-css

Chapter 2, “Brief R Recap"

Chapter 3, “stringr and RegExes”

Chapters 4 and 5, “Crawling the Web” and “Scraping the Web – Extracting Data"

Chapter 6, “Text Preprocessing and Featurization"

Chapter 7, “Supervised Classification"

Chapter 8, "Unsupervised Classification"

Chapter 9, “Word Embeddings”

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Felix Lennert @felixlennert.bsky.social · 21/11/2023

In case you are interested in NLP and how to use it for the social sciences: tomorrow, November 22, we will welcome Isabelle Augenstein in our biweekly seminar. She will talk about “Transparent Cross-Domain Stance Detection.” Check this link for more info: www.css.cnrs.fr/nlp-social-s...

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Marc Keuschnigg @marckeuschnigg.bsky.social · 20/11/2023

The 2024 Conference of the International Network of Analytical Sociologists will take place May 30–31 2024 in Leipzig, Germany. Please visit our conference website www.sozphil.uni-leipzig.de/en/inas-conf... The call for submissions is now open (until Feb. 16). Happy to hear from you!

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Felix Lennert @felixlennert.bsky.social · 07/11/2023

Our reading group on NLP & social sciences will welcome Yiwei Luo on Zoom tomorrow, Nov 8, 17.15 (Paris time). She's going to talk about stance detection (arxiv.org/abs/2010.15149). Our website is down right now, but please feel free to contact me if you want to attend. Lots of love to y'all, Felix

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CREST Sociology @crestsociology.bsky.social · 31/10/2023

CREST Sociology is HIRING! Tenure track or associate professor level, open field! Deadline January 31, 2023! Details here: crest.science/wp-content/u...

aculty Position in Sociology at ENSAE Paris-CREST
ENSAE Paris and CREST are currently inviting applications for a position of Assistant or Associate Professor in
Sociology.
ENSAE Paris is one of the leading French Grande Écoles, specialized in Economics, Data Science, Quantitative Social
Sciences, among other areas. CREST is the associated interdisciplinary center for research on quantitative methods
applied to the social sciences. Both institutions are part of the Institut Polytechnique de Paris, a cluster of graduate schools,
located on the campus of Ecole Polytechnique in the south of Paris.
Sociologists at ENSAE Paris-CREST use empirical data and a diverse range of methods, including quantitative and mixed
methods, to study a wide range of questions. We have a strong expertise in methodology and a rich practice with national
and international datasets and digital data. Our current work addresses questions of social mobility and inequality;
demography; gender, sexuality, and family;

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Felix Lennert @felixlennert.bsky.social · 23/10/2023

Etienne Ollion (on Twitter): Cette semaine au séminaire NLP & Sciences sociales, nous recevons Pierre-Carl Langlais (pour une présentation intitulée "De l’opérationnalisation au fine-tuning : créer des LLM pour l’analyse de corpus en sciences sociales". Détails: css.cnrs.fr/nlp-social-s...

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Felix Lennert @felixlennert.bsky.social · 17/10/2023

before starting beginning the PhD of 3rd year

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Chris Bail @chrisbail.bsky.social · 08/10/2023

Repost if you’ve participated in a Summer Institute in Computational Social Science. Let’s get #SICSS Bluesky going!

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Felix Lennert @felixlennert.bsky.social · 04/10/2023

I'm currently preparing my "toolbox CSS" intro slides and came – again – over this gem of an article. Maybe master's students appreciate this sort of humor, last year's bachelor's didn't even chuckle (source: archive.org/details/Onli...)

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