Mia Costa

Good info in this Experiments newsletter, including: AI/LLM respondents, conjoints in rural development settings, repeated measure designs, & when and why to prioritize data quality over representativeness (from me and John).
⬇️ I'll send you the pdf if link is gated. :)

screenshot of the top of the first page of the fall 2025 experiments section newsletter

There's a new issue of the section newsletter out! This one's on sample considerations in experiments: professional survey-takers, LLM usage, rural contexts, and more!

connect.apsanet.org/s42/newslett...

If we don’t like polarizing politicians, why do we get them?

Negative partisan rhetoric gets the retweets, but not the voters

New #ScienceOfPolitics podcast/transcript with Mia Costa
www.niskanencenter.org/if-we-dont-l...

That'd be great. Sent a DM!

Thank you! 😀

How Politicians Polarize: Political Representation in an Age of Negative Partisanship (Chicago Studies in American Politics) Amazon.com: How Politicians Polarize: Political Representation in an Age of Negative Partisanship (Chicago Studies in American Politics): 9780226838946: Costa, Mia: Books

There's lots more in the book – about how and why representatives shape polarization, what voters respond to and what they don't, and why it matters.

Available here:

Amazon: www.amazon.com/How-Politici...

Chicago: press.uchicago.edu/ucp/books/bo...

Voters don't like when politicians use partisan attacks. But... they think the other side does.

"*I* may not thrive on partisan hostility, but others surely do."

This continues the cycle, leading to a breakdown in political trust and civility.

Politicians talk about policy a lot more than they make partisan attacks! But talking about the out-party gets way, way more attention.

Out-party language gets more likes and retweets, tv news coverage, and campaign donations.

Legislators who attack the other party are worse at their jobs.

Negative representation has clear implications for substantive representation. Both ideological extremity and ineffective lawmaking increase with out-party rhetoric.

Negative partisan rhetoric, while not as common as people think (or see), reinforces a cycle of polarization. And a lot of partisan language is actually completely absent from policy language, especially on Twitter. I show when and why it happens.

My book is now officially out! How Politicians Polarize introduces and documents the concept of "negative representation" – when representatives focus on the other side rather than their own.

Some key findings: 🧵

www.amazon.com/How-Politici...

5/6 🧵 In @ajpseditor.bsky.social @miacosta.bsky.social & @miguelpereira.bsky.social study how occupational backgrounds shape MPs' ability to garner support for their policies. Survey experiments in 🇩🇪 🇺🇸 🇸🇪. Find some experience credibility bonus among citizens & politicians. doi.org/pbhp

Why parties can benefit from promoting occupational diversity in legislatures: Experimental evidence from three countries by Mia Costa and Miguel M. Pereira is now available in Early View. @miacosta.bsky.social @miguelpereira.bsky.social ajps.org/2025/02/26/w...

This might create incentives for elites to stoke fears about other side. But it could also result in less polarized candidates if otherwise ideological prim voters elevate other considerations. Of course this is all conditional on having a competitive general election & good info about electability

We suspect (but don't test) that this helps explain primary dynamics like Biden in 2020. This was the original motivation for the project. Fear and hatred of the other side elevates stakes of election, which in turn elevates importance of electability/elite cues about this trait in nominations

Here we show results from 2 conjoints. 1) shows marginal effect of being "likely to win" (vs lose) on vote choice based on out-party ratings, controlling for ideology alignment. 2) shows win vs. toss up, controlling for policy agreement. Electability always matters most for negative partisans

Winning At All Costs? How Negative Partisanship Affects Voter Decision-Making - Political Behavior Do voters who dislike the other side prefer candidates who can win, even if they are less representative? Negative partisanship is an important feature of American politics, but few scholars have exam...

New @polbehavior.bsky.social paper with @miacosta.bsky.social. We show that voters with more negative views of the other party (negative partisans) are more likely to care about candidate electability & even willing to give up representation for better chance to win
link.springer.com/article/10.1...

Being Careful with Conjoints: Accounting for Inattentiveness in Conjoint Experiments In typical survey experiments–i.e., experiments that involve a relatively limited amount of manipulated content–respondent inattentiveness tends to bias treatment effect estimates toward zero. Such bi...

🚨 Now up on @APSA_Preprints, my paper w/ the great @miacosta.bsky.social on how to deal with inattentiveness in conjoint experiments. Details below! 👇

preprints.apsanet.org/engage/apsa/...

Republicans who stand up to Trump are regularly terrorized by their fellow partisans. It’s a commonly known consequence, but we don’t hear much about it.

Why do we lack parity in gender representation in Congress? One reason is "party-driven descriptive representation." Nearly half of D candidates are women compared to 1 in 6 for R's.

My first post on BlueSky. Hi! My book, HOW POLITICIANS POLARIZE, officially has a cover and I wanted to share. Coming soon in 2025 with University of Chicago Press --> press.uchicago.edu/ucp/books/bo...

Going to #APSA2024? Come check out this great panel Sunday, featuring new work by @miacosta.bsky.social & myself.

In it, we offer a simple way to capture respondent inattentiveness in conjoint experiments & w/o risking post-treatment bias (CC @brendannyhan.bsky.social). Hope to see u there! polisky

Job alert: A little late to the game, but we're searching for a tenure-track assistant prof in comparative politics. We're particularly interested in scholars who study East Asia, Southeast Asia, and/or South Asia.

Details: apply.interfolio.com/151639

Data Scientist Reporting to the chairs of the Departments of Economics, Government and Quantitative Social Sciences, the Data Scientist working in the Social Science Data and Computation Lab at Dartmouth College ser...

We're hiring two data scientists in the Social Science Data and Computing Lab here at Dartmouth. New staff would work with faculty and students. MA preferred, though BA/BS + relevant skills also considered. Some remote (1-2 days a week) possible.

Please share widely!