“Echo Chambers, Filter Bubbles, and Polarization: a Literature Review”, 2022-01-19 (; similar):
Terms like echo chambers, filter bubbles, and polarization are widely used in public and political debate but not in ways that are always aligned with, or based on, scientific work. And even among academic researchers, there is not always a clear consensus on exact definitions of these concepts.
In this literature review we examine, specifically, social science work presenting evidence concerning the existence, causes, and effect of online echo chambers and consider what related research can tell us about scientific discussions online and how they might shape public understanding of science and the role of science in society.
Echo chambers, filter bubbles, and the relationship between news and media use and various forms of polarization has to be understood in the context of increasingly digital, mobile, and platform-dominated media environments where most people spend a limited amount of time with news and many internet users do not regularly actively seek out online news, leading to large inequalities in news use.
When defined as a bounded, enclosed media space that has the potential to both magnify the messages delivered within it and insulate them from rebuttal, studies in the UK estimate that 6–8% of the public inhabit politically partisan online news echo chambers.
More generally, studies both in the UK and several other countries, including the highly polarized US, have found that most people have relatively diverse media diets, that those who rely on only one source typically converge on widely used sources with politically diverse audiences (such as commercial or public service broadcasters) and that only small minorities, often only a few percent, exclusively get news from partisan sources.
Studies in the UK and several other countries show that the forms of algorithmic selection offered by search engines, social media, and other digital platforms generally lead to slightly more diverse news use—the opposite of what the “filter bubble” hypothesis posits—but that self-selection, primarily among a small minority of highly partisan individuals, can lead people to opt in to echo chambers, even as the vast majority do not.
Research on polarization offers a complex picture both in terms of overall developments and the main drivers and there is in many cases limited empirical work done outside the United States. Overall, ideological polarization has, in the long run, declined in many countries but affective polarization has in some, but not all, cases increased. News audience polarization is much lower in most European countries, including the United Kingdom. Much depends on the specifics of individual countries and what point in time one measures change from and there are no universal patterns.
There is limited research outside the United States systematically examining the possible role of news and media use in contributing to various kinds of polarization and the work done does not always find the same patterns as those identified in the US. In the specific context of the United States where there is more research, it seems that exposure to like-minded political content can potentially polarize people or strengthen the attitudes of people with existing partisan attitudes and that cross-cutting exposure can potentially do the same for political partisans.
Public discussions around science online may exhibit some of the same dynamics as those observed around politics and in news and media use broadly, but fundamentally there is at this stage limited empirical research on the possible existence, size, and drivers of echo chambers in public discussions around science. More broadly, existing research on science communication, mainly from the United States, documents the important role of self-selection, elite cues, and small, highly active communities with strong views in shaping these debates and highlights the role especially political elites play in shaping both news coverage and public opinion on these issues.
In summary, the work reviewed here suggests echo chambers are much less widespread than is commonly assumed, finds no support for the filter bubble hypothesis and offers a very mixed picture on polarization and the role of news and media use in contributing to polarization.
…Across a range of different countries, including the highly polarize United States, several cross-platform studies—both those reliant on survey data and those reliant on passive tracking data—have found that few people occupy politically partisan online news echo chambers.
One recent study ( et al 2021b), that includes the UK, used survey data from 2020 to assess the number of people in politically partisan online news echo chambers in Austria, Denmark, Germany, Norway, Spain, the UK, and the US by looking at how many people only use news sources with left-leaning or right-leaning slants (measured in terms of the overall ideological slant of each outlet’s audience). In the UK, the proportion of people estimated to be in a left-leaning echo chamber is around 2% and the proportion in a right-leaning echo chamber is around 5% ( et al 2021b). This is slightly lower than in most of the other countries covered in the study. In most other cases, a minority of around 5% of people only use news sources with ideological slants in one direction. The US is the main outlier among the 7 and the only one where more than 10% of the respondents are estimated to rely only on partisan news sources. In every country covered by this study, many more internet users consume no online news at all on a regular basis than inhabit politically partisan echo chambers. The UK results from this study are broadly similar to a previous analysis, also based on survey data, that, using a more indirect measure of diversity of news use, found that around 10% in the UK said they almost never see political content on social media that they disagree with (2018). In the UK, Fletcher et al (2020c) find a relative dearth of partisan online news echo chambers in the UK, using web tracking data collected during the 2019 General Election and show that the proportion of people in like-minded echo chambers in the UK during the election was 2% among Labour voters and 4% among Conservative voters—very similar to the results of survey-based work in the UK cited above.
These findings are consistent with several other studies of other European countries. In Sweden, for instance, Dahlgren et al (2019, p. 170) found that while some people did engage in selective exposure to partisan news sources, rates were low overall, “suggesting a pattern of cross-cutting exposure more than isolated echo chambers.” The authors note that “citizens who are frequent users of online news from one side of the ideological spectrum also tend to be more frequent users of news from the other side” (p. 170). Similarly, in Spain, et al 2020 did not find strong evidence for widespread news echo chambers and observed that most people accessed “non-like-minded media” at least sometimes. In the Netherlands, et al 2016 found some evidence of partisan selective exposure to news but noted that the formation of echo chambers was largely undercut by people’s common use of relatively impartial public service broadcasting. This is also an important factor in the UK, where the BBC News website is by far the most widely used online news source ( et al 2021b).
Even in the United States, researchers have long found that echo chambers are smaller and less prevalent than commonly assumed. Gentzkow and Shapiro (201113ya, p. 1831193ya) observe that “internet news consumers with homogeneous news diets are rare”, and Garrett (201311ya, p. 248) similarly argues that the notion that large numbers of people are cocooned in pure ideological news echo chambers, cut off from other points of view, is exaggerated and wrong. Studies based on passive tracking that automatically log people’s behavior on one or more platforms have similar findings to analyses of survey data from nationally representative samples, though there are fewer such studies from outside the United States.
Similarly, in Israel, Dvir- et al 2016, using web tracking data collected around the time of the 2013 election, estimate that 3% of people were in an entirely one-sided partisan media echo chamber and that, in most cases, people in Israel had either relatively diverse media diets or did not consume online news at all.
In addition to people’s common use of relatively impartial public service broadcasting undercutting the existence of partisan echo chambers, we should keep in mind that—at least online—their potential size is limited by the fact that many people do not consume much online news in the first place. In the UK, around 25% of internet users say they access no online news at all each week ( et al 2021).
Related research—often not specifically aiming to measure the size of echo chambers—often arrives at broadly similar conclusions by analysing patterns of media use. Again, even in the polarised United States, the results are largely similar. Using network analysis and combining TV and internet tracking data, 2012 find high degrees of audience overlap across news sources and concentration of audiences on large mainstream outlets. Guess (2016, pp. 17–18) observes, based on analysis of tracking data, that there is a “remarkable degree of balance in respondents’ overall media diets regardless of partisan affiliation. Whether Democrat, Republican, or independent, the large bulk of these individuals’ media diets cluster around the center of the ideological spectrum.” Similarly, 2017 find that audiences are concentrated on a few popular political news sites and that, in general, political news sites, irrespective of popularity, have ideologically diverse audiences. et al 2020, working with desktop and mobile data from Comscore’s panels, also observe that ideologically diverse US audiences converge on mainstream news outlets online, find little evidence of ideological selective exposure and, contrary to what some have suggested, find increasing co-exposure to news sources over time. Reinforcing the results from survey data, the authors also note that many more internet users consume no online news at all than rely solely on partisan sources. Single-platform studies are, as noted, of limited value in identifying echo chambers, but there are several important studies that identify like-minded communities formed on individual social media platforms—whether through algorithmic selection, self-selection, or some combination thereof ( et al 2015; et al 2015; 2020; et al 2016). Even these, however, often conclude, like Barberá (2015, p. 28), that “most social media users receive information from a diversity of viewpoints.” And in the absence of evidence on what other media the individuals involved use in addition to the social media platform in question, these studies simply cannot establish whether people inhabit a bounded, enclosed media space where specific messages are magnified and insulated from rebuttal.
In summary, studies in the UK and several other countries, including the highly polarised US, have found very similar results whether relying on survey data or passive tracking data. Most people have diverse media diets, those who rely on only one source typically converge on large sources with politically diverse audiences such as commercial or public service broadcasters, and only small minorities, often only a few percent, exclusively get news from partisan sources.
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In terms of distribution, algorithmic selection by digital platforms such as search engines and social media that make personalized display decisions for countless users using automated systems might, some fear, generate filter bubbles by reducing the diversity of information people come across, serving them more attitude-consistent news and resulting in less cross-cutting exposure.
But empirical studies, whether based on survey data or passive tracking data, have generally found the opposite. They demonstrate that reliance on secondary gatekeepers such as search engines and social media—whatever other problems might be associated with them—is in most cases associated with more diverse news use. This is a consistent finding across a growing number of survey-based studies (2018; 2018a; 2018b; et al 2018) and studies based on various forms of passive tracking data ( et al 2016; et al 2019; et al 2021a; et al 2020; et al 2021). These findings also hold across different countries (including the United Kingdom and the United States), across different digital platforms (search engines, different social media platforms, and news aggregators), and across different methods and modes of analysis. These avenues particularly increase exposure for people who are less likely to otherwise visit news sites directly (2018a; et al 2021). We are not aware of any comparable studies that have found support for the filter bubble hypothesis that algorithmic ranking leads to echo chambers (see 2019 for a more detailed overview).
To understand why algorithmic selection is consistently found to lead to more diverse news diets, not narrower diets (let alone echo chambers), it is important to remember that the median number of different sources of news that people in the UK use on a weekly basis offline is 2, and just one online ( et al 2021). Search engines and social media do not vastly expand this number and it is not the case that people who use these platforms have very diverse and balanced news diets. Rather, they lead people to slightly more, and slightly more diverse, sources of news than what they seek out of their own volition.