On October 28, 2021, the November 2020 paper “Evaluating the scale, growth, and origins of right-wing echo chambers on YouTube” was cited in a hearing of the U.S. Senate Committee on Homeland Security and Governmental Affairs. Authored by PennMAP project lead Homa Hosseinmardi and co-authors Amir Ghasemian, Aaron Clauset, David Rothschild, Markus Mobius, and CSSLab Director Duncan Watts, the paper investigates claims that the YouTube recommendation algorithm systematically directs users towards radical right-wing content.

Last week’s Senate committee hearing examined social media platforms’ role in the amplification of domestic extremism and other harmful content. Among the expert witnesses was Dr. Nate Persily, Co-Director of the Stanford Cyber Policy Center and James B. McClathy Professor of Law at Stanford Law School, who emphasized the need for national transparency legislation targeted towards social media platforms. Citing Hosseinmardi et al.’s paper, he underscored the consequences of harmful online content and argued that it is crucial for “researchers, other than those tied to the profit-maximizing mission of [social media] firms, to get access to the data that will shed light on the most pressing questions related to the effects of social media on society.”

While Hosseinmardi et al.’s paper finds no evidence that the YouTube recommendation algorithm is directly to blame for radical echo chambers, it sheds light upon the size, intensity, and growth of these communities which resonates with calls for increased platform transparency. Using large-scale longitudinal data, the authors analyze YouTube’s role in the broader information ecosystem, finding that the platform largely reflects the tastes and intentions that users enter with.

After being initially released on arXiv in November 2020, their work was published in PNAS in August 2021 under the title “Examining the consumption of radical content on YouTube.”