Cognitive–motivational mechanisms of political polarization in social-communicative contexts

In the paper

“Thus, from a social psychological perspective, group polarization is a dynamic property of a single social group — a shifting of group behaviour over time in a more extreme direction, but in the same direction in which the group started. It is not, strictly speaking, a property of individuals”

What the sources say

• Disputed

  The Abstract (page not supplied) defines group polarization as a change in individual preferences from before to after group discussion, in the direction favored by the group's average prediscussion preferences. This supports the directional-shift aspect, but contradicts the claim that polarization is not, strictly speaking, a property of individuals. Experiment 3’s Results (page not supplied) also calculate polarization scores from individuals’ attitude changes. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  cites [19] Sieber, J. & Ziegler, R. Group polarization revisited: a processing effort account. Pers. Soc. Psychol. Bull. 45, 1482–1498 (2019). sourceExperimental — accuracy not yet measured

In the paper

“Many people, it seems, are amenable to having their misperceptions of the other side corrected, which lowers affective polarization150,153,154.”

What the sources say

• ?Not checked — no full text of the sourcecites [150] Ahler, D. J. & Sood, G. The parties in our heads: misperceptions about party composition and their consequences. J. Polit. 80, 964–981 (2018). source
• ?Not checked — no full text of the sourcecites [153] Druckman, J. N., Klar, S., Krupnikov, Y., Levendusky, M. & Ryan, J. B. (Mis-) estimating affective polarization. J. Polit. 84, 1106–1117 (2022). source
• Disputed

  The Discussion reports that correcting misperceptions about out-party support for violence reduced support for partisan violence, but had no effect on measures of affective polarization in Study 3. The claimed reduction in affective polarization is therefore contrary to this paper’s finding. (LLM, conf=0.91)

  Checked by a reasoning model — may be wrong.

  cites [154] Mernyk, J. S., Pink, S. L., Druckman, J. N. & Willer, R. Correcting inaccurate metaperceptions reduces Americans’ support for partisan violence. Proc. Natl Acad. Sci. USA 119, e2116851119 (2022). sourceExperimental — accuracy not yet measured

In the paper

“These market incentives both reflect and exacerbate ideological and affective forms of polarization, insofar as emotionally charged material, such as that which is contemptuous of ideological adversaries, is more likely to go ‘viral’ than more measured types of political discourse260,263,269,270.”

What the sources say

• Partly supported

  Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [260] Rathje, S., Van Bavel, J. J. & van der Linden, S. Out-group animosity drives engagement on social media. Proc. Natl Acad. Sci. USA https://doi.org/10.1073/pnas.2024292118 (2021). This study of social media platforms finds that messages expressing negative emotions (such as anger, moral outrage and mockery) about the ideological out-group were especially likely to be shared on Facebook and Twitter, compared to other types of message. sourceExperimental — accuracy not yet measured
• Disputed

  Split into 2 atoms — 0 confirmed, 0 partially supported, 2 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Checked by a reasoning model — may be wrong.

  cites [263] Kim, T. Violent political rhetoric on Twitter. Political Sci. Res. Methods. https://doi.org/10.1017/psrm.2022.12 (2022). sourceExperimental — accuracy not yet measured
• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [269] Brady, W. J., Wills, J., Jost, J. T., Tucker, J. & Van Bavel, J. J. Emotion shapes the diffusion of moralized content in social networks. Proc. Natl Acad. Sci. USA 114, 7313–7318 (2017). This study shows that moral-emotional language in political messages diffuse at high rates within (but not between) ideological groups on social media, showing how social media can affect polarization through immersion in an ideological network. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [270] Brady, W. J., Wills, J. A., Burkart, D., Jost, J. T. & Van Bavel, J. J. An ideological asymmetry in the diffusion of moralized content on social media among political leaders. J. Exp. Psychol. Gen. 148, 1802–1813 (2019). source

In the paper

“Whereas conservative-rightist ideology is associated with valuing tradition, social order and maintenance of the status quo, liberal-leftist ideology is associated with a push for egalitarian social change.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [107] Jost, J. T. Left And Right: The Psychological Significance Of A Political Distinction (Oxford Univ. Press, 2021).
• ?Not checked — no full text of the sourcecites [149] Eibach, R. Ideological polarization and social psychology. Oxford Res. Encyc. Psychol. https://doi.org/10.1093/acrefore/9780190236557.013.240 (2021). source
• ?Not checked — no full text of the sourcecites [163] Sidanius, J. & Liu, J. H. The Gulf War and the Rodney King beating: implications of the general conservatism and social dominance perspectives. J. Soc. Psychol. 132, 685–700 (1992). source
• ?Not checked — no full text of the sourcecites [164] Duckitt, J. A dual-process cognitive-motivational theory of ideology and prejudice. Adv. Exp. Soc. Psychol. 33, 41–113 (2001). source
• Partly supported

  The paper’s discussion of right-wing ideologies describes resistance to change and social conservatism, and its section on European far-right followers says supporters tend to resist cultural change and endorse inequality. It associates lower authoritarianism and social-dominance scores with left-wing support, but does not say that liberal-leftist ideology pushes for egalitarian social change. Page numbers are unavailable in our copy. (LLM, conf=0.85)

  cites [165] Van Assche, J., Dhont, K. & Pettigrew, T. F. The social-psychological bases of far-right support in Europe and the United States. J. Commun. Appl. Soc. 29, 385–401 (2019). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [166] Womick, J., Rothmund, T., Azevedo, F., King, L. A. & Jost, J. T. Group-based dominance and authoritarian aggression predict support for Donald Trump in the 2016 US presidential election. Soc. Psychol. Pers. Sci. 10, 643–652 (2019). source
• ?Not checked — no full text of the sourcecites [167] Forscher, P. S. & Kteily, N. S. A psychological profile of the alt-right. Perspect. Psychol. Sci. 15, 90–116 (2020). source
• ?Not checked — no full text of the sourcecites [168] Nilsson, A. & Jost, J. T. The authoritarian-conservatism nexus. Curr. Opin. Behav. Sci. 34, 148–154 (2020). source
• ?Not checked — no full text of the sourcecites [169] Knuckey, J. & Hassan, K. Authoritarianism and support for Trump in the 2016 presidential election. Soc. Sci. J. 59, 47–60 (2022). source

In the paper

“The first has to do with persuasive argumentation: during group discussion, people are exposed to additional arguments in favour of the position that the average group member was already inclined to take19,20.”

What the sources say

• Supported

  The Persuasive Arguments Theory (PAT) section says that, when a group has a prediscussion tendency, discussion is likely to bring up more arguments favoring that already dominant direction. It explains that this shifts the balance of arguments individuals consider and polarizes their opinions. (LLM, conf=0.94)

  cites [19] Sieber, J. & Ziegler, R. Group polarization revisited: a processing effort account. Pers. Soc. Psychol. Bull. 45, 1482–1498 (2019). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [20] Gilovich, T., Keltner, D., Chen, S. & Nisbett, R. E. Social Psychology Revised edn (W. W. Norton, 2016).

In the paper

“For example, there is a strong consensus among scholars of politics in the USA that liberal and conservative political elites (including members of Congress, party activists, donors and judicial appointees) have grown increasingly polarized over the past few decades27–34.”

What the sources say

• ?Not checked — no full text of the sourcecites [27] Layman, G. C., Carsey, T. M. & Horowitz, J. M. Party polarization in American politics: characteristics, causes, and consequences. Annu. Rev. Polit. Sci. 9, 83–110 (2006). source
• Supported

  In this multi-citation sentence, Poole and Rosenthal support the claim about members of Congress. Their discussion of party polarization in Congress states that polarization increased sharply over the preceding thirty years, with Republicans moving right and the Democratic contingent becoming more liberal. The supplied passages do not specify page numbers. (LLM, conf=0.91)

  cites [28] Poole, K. T. & Rosenthal, H. On party polarization in congress. Daedalus 136, 104–107 (2007). source
• ?Not checked — no full text of the sourcecites [29] Fiorina, M. P. & Abrams, S. J. Political polarization in the American public. Annu. Rev. Polit. Sci. 11, 563–588 (2008). source
• ?Not checked — no full text of the sourcecites [30] Bonica, A. Mapping the ideological marketplace. Am. J. Polit. Sci. 58, 367–386 (2014). source
• ?Not checked — no full text of the sourcecites [31] Hare, C. & Poole, K. T. The polarization of contemporary American politics. Polity 46, 411–429 (2014). source
• ?Not checked — no full text of the sourcecites [32] Abramowitz, A. I. The Great Alignment: Race, Party Transformation, and the Rise of Donald Trump (Yale Univ. Press, 2018). source
• ?Not checked — no full text of the sourcecites [33] Neal, Z. P. A sign of the times? Weak and strong polarization in the US Congress, 1973–2016. Soc. Netw. 60, 103–112 (2020). source
• ?Not checked — no full text of the sourcecites [34] Bonica, A. & Sen, M. Estimating judicial ideology. J. Econ. Perspect. 35, 97–118 (2021). source

In the paper

“It refers to the oft-observed tendency for members of a social group to arrive at a consensus (through group discussion and other forms of social interaction) that is more extreme but in the same direction as the average of their initial opinions on a given issue19.”

What the sources say

• Partly supported

  The paper’s Abstract (page unavailable) defines group polarization as a postdiscussion shift in individual preferences toward the direction favored by the group’s average prediscussion preferences. Experiment 3’s Method says participants were asked to reach a consensus, but the paper does not define polarization as arriving at an extreme consensus; it measures individuals’ attitude changes. The consensus element of the citing sentence is therefore not supported as part of the definition. (LLM, conf=0.83)

  cites [19] Sieber, J. & Ziegler, R. Group polarization revisited: a processing effort account. Pers. Soc. Psychol. Bull. 45, 1482–1498 (2019). sourceExperimental — accuracy not yet measured

In the paper

“The body of literature on mass political polarization in the USA has yielded mixed findings: ordinary citizens are deeply divided9,31,35,41–49 or they are not10,29,36,50–54; polarization poses a huge threat to democratic functioning3,11,55, is not a problem at all13,56–58 or the nature of the threat is ambiguous7,59,60.”

What the sources say

• ?Not checked — no full text of the sourcecites [9] Abramowitz, A. I. Transformation and polarization: the 2008 presidential election and the new American electorate. Elect. Stud. 29, 594–603 (2010). source
• ?Not checked — no full text of the sourcecites [31] Hare, C. & Poole, K. T. The polarization of contemporary American politics. Polity 46, 411–429 (2014). source
• ?Not checked — no full text of the sourcecites [35] Levendusky, M. The microfoundations of mass polarization. Polit. Anal. 17, 162–176 (2009). source
• ?Not checked — no full text of the sourcecites [41] Abramowitz, A. I. & Saunders, K. L. Is polarization a myth? J. Polit. 70, 542–555 (2008). source
• ?Not checked — no full text of the sourcecites [42] Bafumi, J. & Shapiro, R. Y. A new partisan voter. J. Polit. 71, 1–24 (2009). source
• Supported

  The “Culture War?” section says the evidence and scholarly interpretations of polarization in American public opinion are “highly mixed,” describing both findings of sharp divisions and arguments that polarization is overstated. The citation is attached to the sentence’s question of whether ordinary citizens are deeply divided, not to its separate claims about threats to democratic functioning. Page numbers are unavailable in our copy. (LLM, conf=0.90)

  cites [43] Jacoby, W. G. Is there a culture war? Conflicting value structures in American public opinion. Am. Polit. Sci. Rev. 108, 754–771 (2014). source
• ?Not checked — no full text of the sourcecites [44] Iyengar, S. & Westwood, S. J. Fear and loathing across party lines: new evidence on group polarization. Am. J. Polit. Sci. 59, 690–707 (2015). source
• ?Not checked — no full text of the sourcecites [45] Mason, L. “I disrespectfully agree”: the differential effects of partisan sorting on social and issue polarization. Am. J. Polit. Sci. 59, 128–145 (2015). source
• Supported

  The Abstract says the debate over whether Americans are polarized has opposing sides and that both can be correct because polarization has several forms. The Discussion describes differing implications for political functioning, including concerns about representation and compromise alongside the possibility of increased voting. This supports the claim that findings about the extent and consequences of mass polarization are mixed; it does not require this source to endorse every position listed alongside the other citations. (LLM, conf=0.87)

  cites [46] Lelkes, Y. Mass polarization: manifestations and measurements. Public Opin. Q. 80, 392–410 (2016). source
• ?Not checked — no full text of the sourcecites [47] Lupton, R. N., Smallpage, S. M. & Enders, A. M. Values and political predispositions in the age of polarization: examining the relationship between partisanship and ideology in the United States, 1988–2012. Br. J. Polit. Sci. 50, 1–20 (2017). This study uses over-time data to show that alignment between ideology and partisanship has increased asymmetrically among those with conservative value orientations, presumably owing to Republican discourse emphasizing traditional family values and resistance to social change. source

In the paper

“At the same time, the extent to which elite-level polarization has influenced the belief systems of ordinary citizens remains a matter of debate8,27,35–40.”

What the sources say

• ?Not checked — no full text of the sourcecites [8] Baldassarri, D. & Gelman, A. Partisans without constraint: political polarization and trends in American public opinion. Am. J. Sociol. 114, 408–446 (2008). source
• ?Not checked — no full text of the sourcecites [27] Layman, G. C., Carsey, T. M. & Horowitz, J. M. Party polarization in American politics: characteristics, causes, and consequences. Annu. Rev. Polit. Sci. 9, 83–110 (2006). source
• ?Not checked — no full text of the sourcecites [35] Levendusky, M. The microfoundations of mass polarization. Polit. Anal. 17, 162–176 (2009). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [36] Fiorina, M. P., Abrams, S. J. & Pope, J. C. Culture War? The Myth of a Polarized America 3rd edn (Pearson Longman, 2010).
• ?Not checked — no full text of the sourcecites [37] Layman, G. C., Carsey, T. M., Green, J. C., Herrera, R. & Cooperman, R. Activists and conflict extension in American party politics. Am. Polit. Sci. Rev. 104, 324–346 (2010). source
• ?Not checked — no full text of the sourcecites [38] Levendusky, M. Clearer cues, more consistent voters: a benefit of elite polarization. Polit. Behav. 32, 111–131 (2010). source
• Supported

  The Abstract says scholars actively debate how elite polarization influences polarization among the public and that there is far from a consensus on citizen polarization. This supports the claim that its influence on ordinary citizens remains a matter of debate. (LLM, conf=0.90)

  cites [39] Druckman, J. N., Peterson, E. & Slothuus, R. How elite partisan polarization affects public opinion formation. Am. Polit. Sci. Rev. 107, 57–79 (2013). source
• ?Not checked — no full text of the sourcecites [40] Baldassarri, D. & Park, B. Was there a culture war? Partisan polarization and secular trends in US public opinion. J. Polit. 82, 809–827 (2020). This analysis of trends in public opinion in the USA over time finds partisan polarization on economic and civil rights issues, whereas opinions on moral issues followed a trend of secularization. Both Democrats and Republicans have increasingly adopted more progressive moral views, but Republicans changed their views more slowly than Democrats. source

In the paper

“These mixed findings reflect a literature that has been vague in identifying precise psychological mechanisms and how they operate across social-communicative contexts61.”

What the sources say

• Partly supported

  The Introduction says our psychological grasp of polarization remains limited and that it is unclear at which processing step polarization takes hold, particularly in naturalistic social and political discourse. It also calls for studying interactions between cognition and context. The cited passages do not say that mixed findings on mass polarization result from this lack of precision. (LLM, conf=0.84)

  cites [61] van Baar, J. M. & FeldmanHall, O. The polarized mind in context: interdisciplinary approaches to the psychology of political polarization. Am. Psychol. https://doi.org/10.1037/amp0000814 (2022). sourceExperimental — accuracy not yet measured

In the paper

“This implies either that two groups — such as liberals and conservatives or leftists and rightists — are moving in opposite, more extreme directions (symmetric polarization) or that one group is becoming more extreme than the other (asymmetric polarization10,34,47,48,73–75).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [10] McCarty, N., Poole, K. T. & Rosenthal, H. Polarized America: the Dance of Ideology and Unequal Riches (MIT Press, 2016).
• ?Not checked — no full text of the sourcecites [34] Bonica, A. & Sen, M. Estimating judicial ideology. J. Econ. Perspect. 35, 97–118 (2021). source
• ?Not checked — no full text of the sourcecites [47] Lupton, R. N., Smallpage, S. M. & Enders, A. M. Values and political predispositions in the age of polarization: examining the relationship between partisanship and ideology in the United States, 1988–2012. Br. J. Polit. Sci. 50, 1–20 (2017). This study uses over-time data to show that alignment between ideology and partisanship has increased asymmetrically among those with conservative value orientations, presumably owing to Republican discourse emphasizing traditional family values and resistance to social change. source
• ?Not checked — no full text of the sourcecites [48] Webster, S. W. & Abramowitz, A. I. The ideological foundations of affective polarization in the US electorate. Am. Polit. Res. 45, 621–647 (2017). This article uses survey and experimental data to show that ideological beliefs (polarization) influence affective polarization, especially when it comes to social welfare issues. source
• ?Not checked — no full text of the sourcecites [73] Hacker, J. & Pierson, P. in Solutions to Political Polarization in America (ed. Persily, N.) 59–70 (Cambridge Univ. Press, 2015). source
• ?Not checked — no full text of the sourcecites [74] Grossmann, M. & Hopkins, D. A. Asymmetric Politics: Ideological Republicans and Group Interest Democrats (Oxford Univ. Press, 2016). source
• Partly supported

  Section 1.4 (Overview; page unavailable) describes symmetric polarization as Trump supporters’ views shifting toward his position while detractors’ views shift against it. Sections 1.2 and 1.3 discuss unequal versus comparable political bias between liberals and conservatives. The paper does not establish the claim’s broader definition in terms of two groups moving toward more extreme ideological positions. (LLM, conf=0.82)

  cites [75] Franks, A. S. & Hesami, F. Seeking evidence of the MAGA cult and Trump derangement syndrome: an examination of (a)symmetric political bias. Societies 11, 113 (2021). sourceExperimental — accuracy not yet measured

In the paper

“Finally, affective polarization (Fig. 1c) occurs when members of different social groups (or political parties) hold strong positive or negative attitudes (or feelings) about the groups themselves (not just their policy preferences49,79), owing to ‘in-party love’ and/or ‘out-party animus’80.”

What the sources say

• Supported

  In “Affective Polarization: An Outgrowth of Partisan Social Identity” (p. 2), the paper describes affective polarization as viewing opposing partisans negatively and copartisans positively. It also says in-group/out-group distinctions trigger positive feelings toward the in-group and negative evaluations of the out-group, supporting the cited ‘in-party love’ and ‘out-party animus’ formulation. (LLM, conf=0.92)

  cites [49] Iyengar, S., Lelkes, Y., Levendusky, M., Malhotra, N. & Westwood, S. J. The origins and consequences of affective polarization in the United States. Annu. Rev. Polit. Sci. 22, 129–146 (2019). source
• ?Not checked — no full text of the sourcecites [79] Iyengar, S., Sood, G. & Lelkes, Y. Affect, not ideology: a social identity perspective on polarization. Public. Opin. Q. 76, 405–431 (2012). source
• ?Not checked — no full text of the sourcecites [80] Brewer, M. B. in The Cambridge Handbook of the Psychology of Prejudice (eds Sibley, C. G. & Barlow, F. K.) 90–110 (Cambridge Univ. Press, 2017). source

In the paper

“Other intervention strategies focus on correcting misperceptions, encouraging more complex thinking, and reducing anger and competitive feelings26,131,132.”

What the sources say

• ?Not checked — no full text of the sourcecites [26] Lees, J. & Cikara, M. Understanding and combating misperceived polarization. Phil. Trans. R. Soc. B 376, 20200143 (2021). This article reviews work on false polarization (when partisans hold inaccurate beliefs about the other side), identifies conditions false polarization leads to actual polarization, and suggests why correcting perceptions about the other party’s beliefs can be effective. source
• Partly supported

  The Introduction’s “Incidental Anger” section links anger to intergroup conflict, and the General Discussion says anger inductions might increase actual and perceived partisan differences. This supports the rationale for addressing anger, but the paper does not describe an intervention that reduces anger or competitive feelings. It also does not address correcting misperceptions or encouraging more complex thinking. (LLM, conf=0.80)

  cites [131] Huber, M., Van Boven, L., Park, B. & Pizzi, W. T. Seeing red: anger increases how much Republican identification predicts partisan attitudes and perceived polarization. PLoS ONE 10, e0139193 (2015). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [132] Fernbach, P. M. & Boven, L. V. False polarization: cognitive mechanisms and potential solutions. Curr. Opin. Psychol. 43, 1–6 (2022). This essay addresses how false polarization — where partisans hold false beliefs about the other side — can lead to actual polarization owing to categorical thinking, oversimplification and emotional amplification. source

In the paper

“This suggests the presence of ego-defensiveness: Republicans were not merely indifferent to liberal messaging but actively sought to combat it or to compensate for its anticipated effects.”

What the sources say

• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [127] Bail, C. A. et al. Exposure to opposing views on social media can increase political polarization. Proc. Natl Acad. Sci. USA 115, 9216–9221 (2018). sourceExperimental — accuracy not yet measured

In the paper

“Group-justifying mechanisms, which are central to social identity theory88,90,91,94, involve group-serving tendencies to advance and maintain the interests and assumptions of the in-group against one or more out-groups (‘us versus them’).”

What the sources say

• ?Not checked — no full text of the sourcecites [88] Brewer, M. B. In-group bias in the minimal intergroup situation: a cognitive-motivational analysis. Psychol. Bull. 86, 307 (1979). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [90] Tajfel, H. & Turner, J. C. in Psychology of Intergroup Relations (eds Worchel, S. & Austin, W. A.) 7–24 (Nelson-Hall, 1986).
• ?Not checked — no full text of the sourcecites [91] Mason, L. Uncivil Agreement: How Politics Became Our Identity (Univ. Chicago Press, 2018). source
• Supported

  Section I (p. 5) explains that partisan identities can motivate people to defend group values, resources, and beliefs when competing parties threaten them. Section II (p. 12) explicitly says people resist out-group influence to protect their in-group identity. Together, these passages support the cited description of group-serving, ‘us versus them’ tendencies. (LLM, conf=0.86)

  cites [94] Van Bavel, J. J. & Pereira, A. The partisan brain: an identity-based model of political belief. Trends Cogn. Sci. 22, 213–224 (2018). source

In the paper

“Partisans might also represent their adversaries as more obstructionist95, more ideologically extreme122,151–153, more prejudiced against the in-group55, or more violent154 than they actually are.”

What the sources say

• ?Not checked — no full text of the sourcecites [95] Lees, J. & Cikara, M. Inaccurate group meta-perceptions drive negative out-group attributions in competitive contexts. Nat. Hum. Behav. 4, 279–286 (2020). source
• ?Not checked — no full text of the sourcecites [122] Blatz, C. W. & Mercier, B. False polarization and false moderation: political opponents overestimate the extremity of each other’s ideologies but underestimate each other’s certainty. Soc. Psychol. Pers. Sci. 9, 521–529 (2018). source
• ?Not checked — no full text of the sourcecites [151] Westfall, J., Van Boven, L., Chambers, J. R. & Judd, C. M. Perceiving political polarization in the United States: party identity strength and attitude extremity exacerbate the perceived partisan divide. Perspect. Psychol. Sci. 10, 145–158 (2015). source
• Supported

  The citation is attached to “more ideologically extreme,” not to the separate claims about obstruction, prejudice, or violence. In the section “People Are More Likely to Perceive Opposing Partisans as More Extreme Than Co-Partisans,” the paper reports that Democrats and Republicans each placed opposing partisans at more extreme positions than those partisans actually held. (LLM, conf=0.94)

  cites [152] Levendusky, M. & Malhotra, N. (Mis)perceptions of partisan polarization in the American public. Public Opin. Q. 80, 378–391 (2016). source
• ?Not checked — no full text of the sourcecites [153] Druckman, J. N., Klar, S., Krupnikov, Y., Levendusky, M. & Ryan, J. B. (Mis-) estimating affective polarization. J. Polit. 84, 1106–1117 (2022). source
• Supported

  Citation 154 is attached to “more violent,” not to the other characteristics in the sentence. In Results, Study 1 (page not provided), Democrats and Republicans both significantly overestimated rival partisans’ support for violence, supporting that attributed point. (LLM, conf=0.94)

  cites [154] Mernyk, J. S., Pink, S. L., Druckman, J. N. & Willer, R. Correcting inaccurate metaperceptions reduces Americans’ support for partisan violence. Proc. Natl Acad. Sci. USA 119, e2116851119 (2022). source

In the paper

“belief in climate change, which has declined among Republicans and self-identified conservatives but not among Democrats and self-identified liberals182,183.”

What the sources say

• Partly supported

  The ‘Ideological Divide: Public Opinion Data’ section reports rising polarization and lower climate-change belief among conservatives than liberals in a 2010 survey. It does not establish that belief declined over time among Republicans and conservatives while remaining stable among Democrats and liberals; the surveys quoted do not provide those group-specific trends. No page number is available in our copy. (LLM, conf=0.84)

  cites [182] Jacquet, J., Dietrich, M. & Jost, J. T. The ideological divide and climate change opinion: “top-down” and “bottom-up” approaches. Front. Psychol. 5, 1458 (2014). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [183] Jenkins-Smith, H. C. et al. Partisan asymmetry in temporal stability of climate change beliefs. Nat. Clim. Change 10, 322–328 (2020). source

In the paper

“However, the social context did not affect unobservable health behaviours such as vaccination, nor did it affect Democrats’ behaviour with regard to any outcomes, including masking325.”

What the sources say

• Supported

  In Empirical Strategy and Results (page unavailable), the paper reports no significant association between local partisan context and COVID-19 or flu vaccination for voters of either party. It also reports that Democrats did not change their mask-wearing rate with zip-code partisan composition, after accounting for other variables. The claim matches the paper’s findings for the outcomes it studied. (LLM, conf=0.91)

  cites [325] Baxter-King, R., Brown, J. R., Enos, R. D., Naeim, A. & Vavreck, L. How local partisan context conditions prosocial behaviors: mask wearing during COVID-19. Proc. Natl Acad. Sci. USA 119, e2116311119 (2022). source

In the paper

“These developments have the capacity to exacerbate all three types of polarization, insofar as individuals bring their own political attitudes and beliefs into alignment with those who are spatially proximate329,331 and tend to form negative impressions, including misperceptions, about those with whom they rarely interact332.”

What the sources say

• ?Not checked — no full text of the sourcecites [329] Martin, G. J. & Webster, S. W. Does residential sorting explain geographic polarization? Polit. Sci. Res. Meth. 8, 215–231 (2020). source
• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [331] Brown, J. R., Enos, R. D., Feigenbaum, J. & Mazumder, S. Childhood cross-ethnic exposure predicts political behavior seven decades later: evidence from linked administrative data. Sci. Adv. 7, eabe8432 (2021). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [332] Levendusky, M. Our Common Bonds: Using What Americans Share to Overcome the Partisan Divide (Univ. Chicago Press, 2023). source

In the paper

“Whether offline202–204 or online205–207, people tend to share information and discuss politics with like-minded others, but they are seldom completely cut off from disagreement208.”

What the sources say

• ?Not checked — no full text of the sourcecites [202] Klofstad, C. A., McDermott, R. & Hatemi, P. K. The dating preferences of liberals and conservatives. Polit. Behav. 35, 519–538 (2013). source
• ?Not checked — no full text of the sourcecites [203] Huckfeldt, R., Mendez, J. M. & Osborn, T. Disagreement, ambivalence, and engagement: the political consequences of heterogeneous networks. Polit. Psychol. 25, 65–95 (2004). source
• ?Not checked — no full text of the sourcecites [204] Lee, B. & Bearman, P. Political isolation in America. Netw. Sci. 8, 333–355 (2020). The study documents trends in the composition of political discussion networks and shows that American’s core discussion networks shrink during heated political times. source
• Supported

  Citation 208 is attached to the claim that people are seldom completely cut off from disagreement. Section 4.1 reports mixed ideological audiences for offline news and rejects the view that liberals and conservatives obtain online news only from like-minded sites. Section 4.4 likewise estimates substantial cross-ideology exposure online. (LLM, conf=0.91)

  cites [205] Gentzkow, M. & Shapiro, J. M. Ideological segregation online and offline. Q. J. Econ. 126, 1799–1839 (2011). source
• ?Not checked — no full text of the sourcecites [206] Bakshy, E., Messing, S. & Adamic, L. A. Exposure to ideologically diverse news and opinion on Facebook. Science 348, 1130–1132 (2015). source
• ?Not checked — no full text of the sourcecites [207] Barberá, P., Jost, J. T., Nagler, J., Tucker, J. A. & Bonneau, R. Tweeting from left to right: is online political communication more than an echo chamber? Psychol. Sci. 26, 1531–1542 (2015). This study estimates ideological preferences of 3.8 million Twitter users in the USA and finds that ideological segregation in social media is less extreme than previously thought. Moreover, liberals are more likely than conservatives to engage in cross-ideological dissemination of information online. source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [208] Barberá, P. in Social Media and Democracy: The State of the Field (eds Persily, N. & Tucker, J.) (Cambridge Univ. Press, 2020).

In the paper

“In one study, a randomly assigned group of Facebook users deactivated Facebook for four weeks prior to the 2018 USA midterm election. When compared to a matched control group, deactivation reduced issue polarization, and to a lesser extent, affective polarization271.”

What the sources say

• ?Could not verify

  Split into 2 atoms — 0 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 2 unverifiable. Expand the claim to see per-atom verdicts.

  cites [271] Allcott, H. et al. Polarization and public health: partisan differences in social distancing during the coronavirus pandemic. J. Public Econ. 191, 104254 (2020). sourceExperimental — accuracy not yet measured

In the paper

“emphasizing a superordinate national identity can reduce out-group animus as well as affective and ideological polarization281–283, consistent with social identity theory90,92,139.”

What the sources say

• ?Not checked — no full text of the sourcecites [281] Levendusky, M. Americans, not partisans. J. Polit. 80, 59–70 (2018). source
• ?Not checked — no full text of the sourcecites [282] Talaifar, S. & Swann, W. B., Jr. Deep alignment with country shrinks the moral gap between conservatives and liberals. Polit. Psychol. 40, 657–675 (2019). source
• Partly supported

  Section 2.2 reports that a coronavirus prime improved feelings toward the opposing party and reduced affective polarization. The Discussion proposes a new sense of national unity as a possible mechanism, but the experiment did not isolate an emphasis on national identity, and the paper does not report a reduction in ideological polarization. Page numbers are unavailable in our copy. (LLM, conf=0.87)

  cites [283] Boxell, L., Conway, J., Druckman, J. N. & Gentzkow, M. Affective polarization did not increase during the COVID-19 pandemic. Q. J. Polit. Sci. Forthcoming https://doi.org/10.2139/ssrn.3785328 (2021). sourceExperimental — accuracy not yet measured
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [90] Tajfel, H. & Turner, J. C. in Psychology of Intergroup Relations (eds Worchel, S. & Austin, W. A.) 7–24 (Nelson-Hall, 1986).
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [92] Van Bavel, J. J. & Packer, D. The Power of Us: Harnessing Our Shared Identities to Improve Performance, Increase Cooperation, and Promote Social Harmony (Little Brown Spark, 2021).
• ?Not checked — no full text of the sourcecites [139] Dovidio, J. F., Gaertner, S. L. & Kafati, G. Group identity and intergroup relations: the common in-group identity model. Adv. Group. Process. 17, 1–35 (2000). source

In the paper

“Retweets often included anger-related language260; this is important because anger inflames political polarization by, among other things, increasing cognitive oversimplification and categorical thinking that divides ‘us’ and ‘them.’132.”

What the sources say

• Partly supported

  Citation 260 attaches to the retweets clause, not the later explanation of how anger affects polarization. The Results (Study 1: Major Media Outlets; Study 2: Congress Members) find that negative-affect language is associated with higher retweet rates, but do not establish how often retweets included anger-specific language. Page numbers are unavailable in our copy. (LLM, conf=0.79)

  cites [260] Rathje, S., Van Bavel, J. J. & van der Linden, S. Out-group animosity drives engagement on social media. Proc. Natl Acad. Sci. USA https://doi.org/10.1073/pnas.2024292118 (2021). This study of social media platforms finds that messages expressing negative emotions (such as anger, moral outrage and mockery) about the ideological out-group were especially likely to be shared on Facebook and Twitter, compared to other types of message. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [132] Fernbach, P. M. & Boven, L. V. False polarization: cognitive mechanisms and potential solutions. Curr. Opin. Psychol. 43, 1–6 (2022). This essay addresses how false polarization — where partisans hold false beliefs about the other side — can lead to actual polarization owing to categorical thinking, oversimplification and emotional amplification. source

In the paper

“there is clearly a market for political misinformation255, and technology companies such as Twitter and Facebook profit from the spread of ‘fake news’, which increases customer engagement and therefore advertising revenue256.”

What the sources say

• Partly supported

  The citation is attached to the claim about Twitter and Facebook profiting, rather than the preceding claim about a market for misinformation. “Who Produces Fake News?” says viral stories can earn advertising revenue when users click through to the original site, but attributes that revenue to fake-news producers. “Social Media as a Source of Political Information” describes platforms as conducive to fake-news circulation; it does not establish that Twitter or Facebook profit from it through increased engagement and advertising revenue. (LLM, conf=0.82)

  cites [255] Allcott, H. & Gentzkow, M. Social media and fake news in the 2016 election. J. Econ. Perspect. 31, 211–236 (2017). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [256] Spohr, D. Fake news and ideological polarization: filter bubbles and selective exposure on social media. Bus. Inf. Rev. 34, 150–160 (2017). source

In the paper

“patterns of online ideological segregation resemble offline patterns of media consumption205, and most social media users are exposed to reasonable levels of ideological heterogeneity206,207,257,266–268.”

What the sources say

• Supported

  Citation 205 is attached to the first clause, comparing online segregation with offline media consumption. Section 4.1 states that ideological segregation on the Internet is similar to segregation in other media. The separate claim about social media users has other citations and is not attributed to this source. (LLM, conf=0.94)

  cites [205] Gentzkow, M. & Shapiro, J. M. Ideological segregation online and offline. Q. J. Econ. 126, 1799–1839 (2011). source
• ?Not checked — no full text of the sourcecites [206] Bakshy, E., Messing, S. & Adamic, L. A. Exposure to ideologically diverse news and opinion on Facebook. Science 348, 1130–1132 (2015). source
• ?Not checked — no full text of the sourcecites [207] Barberá, P., Jost, J. T., Nagler, J., Tucker, J. A. & Bonneau, R. Tweeting from left to right: is online political communication more than an echo chamber? Psychol. Sci. 26, 1531–1542 (2015). This study estimates ideological preferences of 3.8 million Twitter users in the USA and finds that ideological segregation in social media is less extreme than previously thought. Moreover, liberals are more likely than conservatives to engage in cross-ideological dissemination of information online. source
• Partly supported

  The cited paper reports evidence suggesting that most social media users remain regularly exposed to opposing standpoints (passage [1], labeled Abstract in our copy). That supports the heterogeneity point, but the citing sentence states it as fact while the paper presents it as a suggestion in a contested debate. The offline-media comparison is attached to a different citation, not this source. (LLM, conf=0.82)

  cites [257] Kligler-Vilenchik, N., Baden, C. & Yarchi, M. Interpretative polarization across platforms: how political disagreement develops over time on Facebook, Twitter, and WhatsApp. Soc. Media Soc. 6, 2056305120944393 (2020). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [266] Hargittai, E., Gallo, J. & Kane, M. Cross-ideological discussions among conservative and liberal bloggers. Public Choice 134, 67–86 (2008). source
• Supported

  The citation is attached to the second clause. In “Reinforcing existing preferences,” the paper says that even on social media, most individuals are exposed to a variety of political views and information sources, supporting the claim of ideological heterogeneity. (LLM, conf=0.88)

  cites [267] Dubois, E. & Blank, G. The echo chamber is overstated: the moderating effect of political interest and diverse media. Inf. Commun. Soc. 21, 729–745 (2018). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [268] Guess, A., Nyhan, B., Lyons, B. & Reifler, J. Avoiding the Echo Chamber About Echo Chambers (Knight Foundation, 2018).

In the paper

“Research to date paints a confusing picture, with some studies indicating a negative relationship between affective polarization and support for democratic norms302,303, and others finding no connection between the two13,58.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [13] Broockman, D. E., Kalla, J. L. & Westwood S. J. Does affective polarization undermine democratic norms or accountability? Am. J. Polit. Sci. (in the press).
• Supported

  The Discussion reports that correlations between affective polarization and three anti-democratic attitudes were not reliable across the studies. The paper does not claim that every measured correlation was zero, but its finding supports the citing sentence’s characterization of no consistent connection with support for democratic norms. (LLM, conf=0.86)

  cites [58] Voelkel, J. G. et al. Interventions reducing affective polarization do not improve anti-democratic attitudes. Nat. Hum. Behav. https://doi.org/10.31219/osf.io/7evmp (2021). source

In the paper

“In general, sharing personal experiences rather than facts appears to foster respect and humanize politicians, even in the eyes of their adversaries, thereby reducing affective polarization292,297.”

What the sources say

• Partly supported

  The General Discussion reports that personal experiences foster more respect for political opponents than facts, and the meta-analyses report greater willingness to interact with them. But the paper says its studies examined everyday Americans and that it is unclear whether the benefits extend to interactions between elected officials. It does not establish that sharing experiences humanizes politicians or reduces affective polarization as a measured outcome. (LLM, conf=0.91)

  cites [292] Kubin, E., Puryear, C., Schein, C. & Gray, K. Personal experiences bridge moral and political divides better than facts. Proc. Natl Acad. Sci. USA 118, e2008389118 (2021). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [297] Carpenter, C. J. Cognitive dissonance, ego-involvement, and motivated reasoning. Ann. Int. Comun. Assoc. 43, 1–23 (2019). source

In the paper

“Research to date paints a confusing picture, with some studies indicating a negative relationship between affective polarization and support for democratic norms302,303, and others finding no connection between the two13,58.”

What the sources say

• Supported

  The paper states that affectively polarized partisans favor co-partisans even when doing so violates democratic norms. Study 3.2, “Tolerance for political corruption,” reports that support for investigating a co-partisan falls as affective polarization rises; it does not find the same relationship for investigations of out-party members. (LLM, conf=0.91)

  cites [302] Lelkes, Y. & Westwood, S. J. The limits of partisan prejudice. J. Polit. 79, 485–501 (2017). source
• ?Not checked — no full text of the sourcecites [303] Kingzette, J. et al. How affective polarization undermines support for democratic norms. Public Opin. Q. 85, 663–677 (2021). source

In the paper

“Experimental studies suggest that increasing system justification motivation may, in some cases, raise the national attachment levels of people who hold liberal views so that they more closely resemble those of people who hold conservative views, thereby temporarily reducing polarization on issues of patriotism — but not nationalism, defined as an attitude of superiority towards other countries282”

What the sources say

• ?Not checked — no full text of the sourcecites [282] Talaifar, S. & Swann, W. B., Jr. Deep alignment with country shrinks the moral gap between conservatives and liberals. Polit. Psychol. 40, 657–675 (2019). source
• ?Not checked — no full text of the sourcecites [287] van der Toorn, J., Nail, P., Liviatan, I. & Jost, J. T. My country, right or wrong: does activating system justification motivation eliminate the liberal–conservative gap in patriotism? J. Exp. Soc. Psychol. 54, 50–60 (2014). source
• Partly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [288] Kobayashi, T. & Katagiri, A. The “rally around the flag” effect in territorial disputes: experimental evidence from Japan–China relations. J. East Asian Stud. 18, 299–319 (2018). sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [289] Porat, R., Tamir, M., Wohl, M. J., Gur, T. & Halperin, E. Motivated emotion and the rally around the flag effect: liberals are motivated to feel collective angst (like conservatives) when faced with existential threat. Cogn. Emot. 33, 480–491 (2019). source

In the paper

“Historically speaking, polarization in the USA reflects social patterns that began with Southern realignment following civil rights legislation, the rise of single-issue interest groups, changes in campaign finance law, and the withdrawal of moderates from party politics and primary races, especially on the political right10,27,31,34,37,72,342,343).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [10] McCarty, N., Poole, K. T. & Rosenthal, H. Polarized America: the Dance of Ideology and Unequal Riches (MIT Press, 2016).
• ?Not checked — no full text of the sourcecites [27] Layman, G. C., Carsey, T. M. & Horowitz, J. M. Party polarization in American politics: characteristics, causes, and consequences. Annu. Rev. Polit. Sci. 9, 83–110 (2006). source
• ?Not checked — no full text of the sourcecites [31] Hare, C. & Poole, K. T. The polarization of contemporary American politics. Polity 46, 411–429 (2014). source
• ?Not checked — no full text of the sourcecites [34] Bonica, A. & Sen, M. Estimating judicial ideology. J. Econ. Perspect. 35, 97–118 (2021). source
• ?Not checked — no full text of the sourcecites [37] Layman, G. C., Carsey, T. M., Green, J. C., Herrera, R. & Cooperman, R. Activists and conflict extension in American party politics. Am. Polit. Sci. Rev. 104, 324–346 (2010). source
• ?Not checked — no full text of the sourcecites [72] McCarty, N. Polarization: What Everyone Needs To Know (Oxford Univ. Press, 2019). source
• ?Not checked — no full text of the sourcecites [342] Thomsen, D. M. Opting Out Of Congress: Partisan Polarization And The Decline Of Moderate Candidates (Cambridge Univ. Press, 2017). source
• Partly supported

  The Development of Modern Political Polarization links modern polarization to party realignment over civil rights, and The Shifting Relationship Between Interest Groups and Parties describes the growth and partisan alignment of interest groups. Shifts in State Parties and Federalism discusses nomination reforms that increased activists’ influence. The passages do not establish changes in campaign finance law or a withdrawal of moderates from party politics and primary races, particularly on the right; they describe reduced moderating influence by party organizations instead. Page numbers were not available in our copy. (LLM, conf=0.87)

  cites [343] Pierson, P. & Schickler, E. Madison’s constitution under stress: a developmental analysis of political polarization. Annu. Rev. Polit. Sci. 23, 37–58 (2020). sourceExperimental — accuracy not yet measured

In the paper

“In Germany, opinions about whether to welcome asylum seekers became highly polarized, with opponents embracing system-justifying stereotypes and exhibiting motivated reasoning on the question of whether asylum seekers increase rates of criminal activity319.”

What the sources say

• Partly supported

  Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [319] Glinitzer, K., Gummer & Wagner, M. Learning facts about migration: politically motivated learning of polarizing information about refugees. Polit. Psychol. https://doi.org/10.1111/pops.12734 (2021). sourceExperimental — accuracy not yet measured

In the paper

“In European countries, there are longstanding territorial, religious and social class cleavages and more recent cleavages pertaining to globalization and integration with the European Union333,334.”

What the sources say

• Supported

  The section ‘The Impact of the New Structural Conflict on the Structure of the Political Space’ (page not supplied) identifies longstanding center–periphery, religious, and owner–worker cleavages. It also identifies newer conflicts linked to globalization, including European integration. The claim is a fair summary of those passages. (LLM, conf=0.91)

  cites [333] Kriesi, H. et al. Globalization and the transformation of the national political space: six European countries compared. Eur. J. Polit. Res. 45, 921–956 (2006). source
• ?Not checked — no full text of the sourcecites [334] Hooghe, L. & Marks, G. Cleavage theory meets Europe’s crises: Lipset, Rokkan, and the transnational cleavage. J. Eur. Public Policy 25, 109–135 (2018). source

In the paper

“For instance, people were more favourable towards a policy proposal when it was described as coming from the in-party rather than the out-party85, suggesting that general group-based attitudes drove issue preferences, thereby leading to issue polarization.”

What the sources say

• ?Not checked — no full text of the sourcecites [85] Cohen, G. L. Party over policy: the dominating impact of group influence on political beliefs. J. Pers. Soc. Psychol. 85, 808–822 (2003). source

In the paper

“However, follow-up research indicated that this was true for Republican but not Democratic supporters86.”

What the sources say

• ?Not checked — no full text of the sourcecites [86] Bullock, J. G. Elite influence on public opinion in an informed electorate. Am. Polit. Sci. Rev. 105, 496–515 (2011). source

In the paper

“Moreover, longitudinal research demonstrated that ideological consistency at time 1 predicted affective polarization at time 2, and affective polarization at time 1 predicted ideological consistency at time 2, all other things being equal82,87.”

What the sources say

• ?Not checked — no full text of the sourcecites [82] Enders, A. M. & Lupton, R. N. Value extremity contributes to affective polarization in the US. Polit. Sci. Res. Meth. 9, 857–866 (2021). source
• ?Not checked — no full text of the sourcecites [87] Lelkes, Y. Affective polarization and ideological sorting: a reciprocal, albeit weak, relationship. Forum 16, 67–79 (2018). source

In the paper

“In feeling thermometer ratings, participants were more affectively polarized in the divergent condition, expressing more warmth towards the more extreme candidate whose ideology they shared and less warmth towards the more extreme candidate whose ideology they did not share. This effect was stronger for participants who were more interested in politics and more ideologically extreme themselves83.”

What the sources say

• ?Not checked — no full text of the sourcecites [83] Rogowski, J. C. & Sutherland, J. L. How ideology fuels affective polarization. Polit. Behav. 38, 485–508 (2016). source

In the paper

“Another series of experiments demonstrated that learning about policy disagreements between rank-and-file Democrats and Republicans made partisan identities more salient and caused participants to express more warmth towards in-party members and less warmth towards out-party members81.”

What the sources say

• ?Not checked — no full text of the sourcecites [81] Dias, N. & Lelkes, Y. The nature of affective polarization: disentangling policy disagreement from partisan identity. Am. J. Polit. Sci. https://doi.org/10.1111/ajps.12628 (2021). source

In the paper

“Consistent with this argument, there is abundant evidence that since the 1960s those who endorse liberal attitudes have increasingly joined the Democratic Party, and those who endorse conservative attitudes have increasingly joined the Republican Party35,110.”

What the sources say

• ?Not checked — no full text of the sourcecites [35] Levendusky, M. The microfoundations of mass polarization. Polit. Anal. 17, 162–176 (2009). source
• ?Not checked — no full text of the sourcecites [110] Noel, H. Political Ideologies and Political Parties in America (Cambridge Univ. Press, 2014). source

In the paper

“By contrast, media coverage that is critical of polarization among political elites can reduce issue polarization among citizens, presumably because people do not want to be seen (by themselves or others) as extremists122,158–160.”

What the sources say

• ?Not checked — no full text of the sourcecites [122] Blatz, C. W. & Mercier, B. False polarization and false moderation: political opponents overestimate the extremity of each other’s ideologies but underestimate each other’s certainty. Soc. Psychol. Pers. Sci. 9, 521–529 (2018). source
• ?Not checked — no full text of the sourcecites [158] Cialdini, R. B., Levy, A., Herman, C. P. & Evenbeck, S. Attitudinal politics: the strategy of moderation. J. Pers. Soc. Psychol. 25, 100–108 (1973). source
• ?Not checked — no full text of the sourcecites [159] Levendusky, M. & Malhotra, N. Does media coverage of partisan polarization affect political attitudes? Polit. Commun. 33, 283–301 (2016). source
• ?Not checked — no full text of the sourcecites [160] Robison, J. & Mullinix, K. J. Elite polarization and public opinion: how polarization is communicated and its effects. Polit. Commun. 33, 261–282 (2016). source

In the paper

“In one study, Republicans overestimated the percentage of Democrats who were LGBTQ by 25 points, whereas Democrats overestimated the percentage of Republicans who were evangelicals by 20 points150.”

What the sources say

• ?Not checked — no full text of the sourcecites [150] Ahler, D. J. & Sood, G. The parties in our heads: misperceptions about party composition and their consequences. J. Polit. 80, 964–981 (2018). source

In the paper

“analyses of historical trends in public opinion from 1972 to 2016 reveal that Democrats were early adopters of more egalitarian views about gender, civil rights and gay rights, as well as more progressive on moral issues, whereas Republicans resisted these secular trends and were slower to change their attitudes40.”

What the sources say

• ?Not checked — no full text of the sourcecites [40] Baldassarri, D. & Park, B. Was there a culture war? Partisan polarization and secular trends in US public opinion. J. Polit. 82, 809–827 (2020). This analysis of trends in public opinion in the USA over time finds partisan polarization on economic and civil rights issues, whereas opinions on moral issues followed a trend of secularization. Both Democrats and Republicans have increasingly adopted more progressive moral views, but Republicans changed their views more slowly than Democrats. source

In the paper

“support for governmental regulation of the economy declined sharply among rank-and-file Republicans between 1984 and 2010, while it remained unchanged among Democrats175.”

What the sources say

• ?Not checked — no full text of the sourcecites [175] Brooks, C. & Manza, J. A broken public? Americans’ responses to the great recession. Am. Sociol. Rev. 78, 727–748 (2013). source

In the paper

“possessing ideologically homogeneous networks exacerbates issue and affective polarization, whereas having a heterogeneous network facilitates the correction of stereotypical misconceptions and decreases polarization223–227.”

What the sources say

• ?Not checked — no full text of the sourcecites [223] Druckman, J. N. & Nelson, K. R. Framing and deliberation: how citizens’ conversations limit elite influence. Am. J. Polit. Sci. 47, 729–745 (2003). source
• ?Not checked — no full text of the sourcecites [224] Klar, S. Partisanship in a social setting. Am. J. Polit. Sci. 58, 687–704 (2014). source
• ?Not checked — no full text of the sourcecites [225] Hart, P. S., Feldman, L., Leiserowitz, A. & Maibach, E. Extending the impacts of hostile media perceptions: influences on discussion and opinion polarization in the context of climate change. Sci. Commun. 37, 506–532 (2015). source
• ?Not checked — no full text of the sourcecites [226] Hutchens, M. J., Hmielowski, J. D. & Beam, M. A. Reinforcing spirals of political discussion and affective polarization. Commun. Monogr. 86, 357–376 (2019). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [227] Rossiter, E. The consequences of interparty conversation on outparty affect and stereotypes. Preprint at http://erossiter.com/files/conversations.pdf (2020).

In the paper

“Elite polarization predated the rise of mass polarization in the USA by several years, suggesting that voters began to ‘catch up’ to party leaders over time10,42,48.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [10] McCarty, N., Poole, K. T. & Rosenthal, H. Polarized America: the Dance of Ideology and Unequal Riches (MIT Press, 2016).
• ?Not checked — no full text of the sourcecites [42] Bafumi, J. & Shapiro, R. Y. A new partisan voter. J. Polit. 71, 1–24 (2009). source
• ?Not checked — no full text of the sourcecites [48] Webster, S. W. & Abramowitz, A. I. The ideological foundations of affective polarization in the US electorate. Am. Polit. Res. 45, 621–647 (2017). This article uses survey and experimental data to show that ideological beliefs (polarization) influence affective polarization, especially when it comes to social welfare issues. source

In the paper

“over the past three decades, Americans’ personal networks have become smaller and more homogeneous in terms of political preferences, apparently because ‘important matters’ are increasingly framed as ideologically meaningful204.”

What the sources say

• ?Not checked — no full text of the sourcecites [204] Lee, B. & Bearman, P. Political isolation in America. Netw. Sci. 8, 333–355 (2020). The study documents trends in the composition of political discussion networks and shows that American’s core discussion networks shrink during heated political times. source

In the paper

“Although exposure to counter-attitudinal news did not change participants’ political opinions, it did reduce affective polarization (compared to a control group), possibly because instructions to participants stressed that new and valuable perspectives would be presented, which might have quelled ego-justifying, group-justifying and system-justifying motives.”

In the paper

“Republican elite discourse has for decades emphasized traditional family values and resistance to social change, and this seems to have increased the correlation between partisanship and ideology more steeply among Republican than Democratic voters47.”

What the sources say

• ?Not checked — no full text of the sourcecites [47] Lupton, R. N., Smallpage, S. M. & Enders, A. M. Values and political predispositions in the age of polarization: examining the relationship between partisanship and ideology in the United States, 1988–2012. Br. J. Polit. Sci. 50, 1–20 (2017). This study uses over-time data to show that alignment between ideology and partisanship has increased asymmetrically among those with conservative value orientations, presumably owing to Republican discourse emphasizing traditional family values and resistance to social change. source

In the paper

“Exposure to ideologically driven networks (such as Fox News on the political right and MSNBC on the political left) exerts both persuasive245,246 and reinforcement effects247.”

What the sources say

• ?Not checked — no full text of the sourcecites [245] DellaVigna, S. & Kaplan, E. The Fox News effect: media bias and voting. Q. J. Econ. 120, 1187–1234 (2007). source
• ?Not checked — no full text of the sourcecites [246] Martin, G. J. & Yurukoglu, A. Bias in cable news: persuasion and polarization. Am. Econ. Rev. 107, 2565–2599 (2017). source
• ?Not checked — no full text of the sourcecites [247] Hopkins, D. J. & Ladd, J. M. The consequences of broader media choice: evidence from the expansion of Fox News. Q. J. Polit. Sci. 9, 115–135 (2014). source

In the paper

“exposure to same-party and other-party messages on partisan media platforms often increases affective polarization, in the latter case because of resistance to change and the spontaneous generation of counterarguments249.”

What the sources say

• ?Not checked — no full text of the sourcecites [249] Druckman, J. N., Gubitz, S. R., Levendusky, M. S. & Lloyd, A. How incivility on partisan media (de-)polarizes the electorate. J. Polit. 81, 291–295 (2019). source

In the paper

“In another experiment, thousands of Facebook users were randomly assigned to subscribe to liberal or conservative news outlets for at least two weeks259. Results of the study confirmed that Facebook’s algorithm limits exposure to counter-attitudinal news in general, but when participants were assigned to receive counter-attitudinal news they were willing to read and share it.”

What the sources say

• ?Not checked — no full text of the sourcecites [259] Levy, R. E. Social media, news consumption, and polarization: evidence from a field experiment. Am. Econ. Rev. 111, 831–870 (2021). source

In the paper

“in 2016, Donald Trump supporters were more likely to justify economic inequality under capitalism and gender disparities under the patriarchal social order, in comparison with supporters of Hillary Clinton, but they were not more likely to justify the general social system in the USA following eight years of Barack Obama’s presidency284.”

What the sources say

• ?Not checked — no full text of the sourcecites [284] Azevedo, F., Jost, J. T. & Rothmund, T. “Making America great again”: system justification in the 2016 U.S. presidential election. Transl. Issues Psychol. Sci. 3, 231–240 (2017). source

In the paper

“Prior to 2000, Democrats and Republicans differed little in terms of nationalist beliefs, but as of 2016 they held very different conceptions, apparently because of 9/11, the wars in Afghanistan and Iraq, and racial resentment in response to Barack Obama’s presidency286.”

What the sources say

• ?Not checked — no full text of the sourcecites [286] Bonikowski, B., Feinstein, Y. & Bock, S. The partisan sorting of “America”: How nationalist cleavages shaped the 2016 US Presidential election. Am. J. Sociol. 127, 492–561 (2021). source

In the paper

“exposure to Joe Biden’s storytelling increased support for social security among Democrats but not Republicans, thereby increasing issue polarization. However, the narrative did increase liking for Biden in all participants291.”

What the sources say

• ?Not checked — no full text of the sourcecites [291] Gooch, A. Ripping yarn: experiments on storytelling by partisan elites. Polit. Commun. 35, 220–238 (2018). source

In the paper

“exposure to overly confrontational, uncivil discourse from members of one’s own party can lead to depolarization; this is because citizens view such rhetoric as norm-violating and wish to distance themselves from the source of the message249.”

What the sources say

• ?Not checked — no full text of the sourcecites [249] Druckman, J. N., Gubitz, S. R., Levendusky, M. S. & Lloyd, A. How incivility on partisan media (de-)polarizes the electorate. J. Polit. 81, 291–295 (2019). source

In the paper

“Ego-justifying and group-justifying motives lead individuals to defend their own pre-existing beliefs and those of their in-group, respectively.”

In the paper

“This type of polarization is typically operationalized as approaching or arriving at a bimodal distribution of beliefs, opinions and values50,72.”

What the sources say

• ?Not checked — no full text of the sourcecites [50] DiMaggio, P., Evans, J. & Bryson, B. Have Americans’ social attitudes become more polarized? Am. J. Sociol. 102, 690–755 (1996). source
• ?Not checked — no full text of the sourcecites [72] McCarty, N. Polarization: What Everyone Needs To Know (Oxford Univ. Press, 2019). source

In the paper

“First, issue or ideological polarization (Fig. 1a) is characterized as moving towards the extremes and away from the centre with respect to issues and/or ideology29.”

What the sources say

• ?Not checked — no full text of the sourcecites [29] Fiorina, M. P. & Abrams, S. J. Political polarization in the American public. Annu. Rev. Polit. Sci. 11, 563–588 (2008). source

In the paper

“There are three operational definitions of mass political polarization (see Fig. 1), which might differ in terms of whether they are psychologically underpinned by cognitive, motivational or affective concerns.”

In the paper

“The second focuses on social comparison processes and conformity to perceived group norms: individuals in a group conform to what they perceive as the group norm.”

What the sources say

• ?Not checked — no full text of the sourcecites [21] Hogg, M. A., Turner, J. C. & Davidson, B. Polarized norms and social frames of reference: a test of the self-categorization theory of group polarization. Basic. Appl. Soc. Psychol. 11, 77–100 (1990). source
• ?Not checked — no full text of the sourcecites [22] McGarty, C., Turner, J. C., Hogg, M. A., David, B. & Wetherell, M. S. Group polarization as conformity to the prototypical group member. Br. J. Soc. Psychol. 31, 1–19 (1992). source
• ?Not checked — no full text of the sourcecites [23] Sinclair, B. The Social Citizen: Peer Networks And Political Behavior (Univ. Chicago Press, 2012). source
• ?Not checked — no full text of the sourcecites [24] Sunstein, C. Conformity: The Power Of Social Influences (New York Univ. Press, 2019). source

In the paper

“We propose that there are at least three general classes of psychological mechanism that contribute to political polarization.”

In the paper

“Second, mass polarization in terms of partisan alignment (Fig. 1b) focuses on the dimensionality of the political space.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [62] Lipset, S. M. & Rokkan, S. in Party Systems and Voter Alignments: Cross-National Perspectives 1–64 (The Free Press, 1967).
• ?Not checked — no full text of the sourcecites [64] Cox, G. W. Making Votes Count: Strategic Coordination in the World’s Electoral Systems (Cambridge Univ. Press, 1997). source
• ?Not checked — no full text of the sourcecites [76] Guth, J. L. & Nelsen, B. F. Party choice in Europe: social cleavages and the rise of populist parties. Party Politics 27, 453–464 (2021). source

In the paper

“(It may be that people do not necessarily hold negative attitudes towards out-party members in particular, but rather towards any person or group that is highly partisan54.)”

What the sources say

• ?Not checked — no full text of the sourcecites [54] Klar, S., Krupnikov, Y. & Ryan, J. B. Affective polarization or partisan disdain? Untangling a dislike for the opposing party from a dislike of partisanship. Public. Opin. Q. 82, 379–390 (2018). source

In the paper

“Ego-justifying mechanisms involve the self-serving tendency to advance and maintain one’s own pre-existing beliefs, opinions and values and to defend against information that might contradict any of those98,99.”

What the sources say

• ?Not checked — no full text of the sourcecites [98] Dunning, D. A newer look: motivated social cognition and the schematic representation of social concepts. Psychol. Inq. 10, 1–11 (1999). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [99] Jost, J. T., Hennes, E. P. & Lavine, H. in The Oxford Handbook of Social Cognition (ed. Carlston, D. E.) 851–875 (Oxford Univ. Press, 2013).

In the paper

“System-justifying mechanisms, which are often overlooked in social psychological analyses of political polarization, reflect the fact that some individuals and groups are motivated to preserve the status quo — and to resist various forms of social change — while others are motivated to challenge or improve upon it100,101.”

What the sources say

• ?Not checked — no full text of the sourcecites [100] Jost, J. T. Resistance to change: a social psychological perspective. Soc. Res. 82, 607–636 (2015). source
• ?Not checked — no full text of the sourcecites [101] Jost, J. T. A Theory of System Justification (Harvard Univ. Press, 2020). source

In the paper

“Additional cognitive–motivational mechanisms that may exacerbate issue polarization include other forms of reduction in cognitive dissonance, such as selective avoidance of counter-attitudinal information and motivated resistance to attitude change (see Table 1), both of which reflect ego-defensive motives to avoid inconsistency and maintain the individual’s pre-existing beliefs, opinions and”

What the sources say

• ?Not checked — no full text of the sourcecites [100] Jost, J. T. Resistance to change: a social psychological perspective. Soc. Res. 82, 607–636 (2015). source
• ?Not checked — no full text of the sourcecites [123] Greenwald, A. G. The totalitarian ego: fabrication and revision of personal history. Am. Psychol. 35, 603–618 (1980). source
• ?Not checked — no full text of the sourcecites [124] Vraga, E. K. How party affiliation conditions the experience of dissonance and explains polarization and selective exposure. Soc. Sci. Q. 96, 487–502 (2015). source
• ?Not checked — no full text of the sourcecites [125] Harmon-Jones, E., & Mills, J. in Cognitive Dissonance: Reexamining a Pivotal Theory in Psychology 3–24 (American Psychological Association, 2019). source
• ?Not checked — no full text of the sourcecites [126] Stanley, M. L., Henne, P., Yang, B. W. & De Brigard, F. Resistance to position change, motivated reasoning, and polarization. Polit. Behav. 42, 891–913 (2020). source

In the paper

“From a more macro-political perspective, increased alignment between partisanship and ideology reflects a ‘sorting’ process that increases intergroup conflict35,38,77.”

What the sources say

• ?Not checked — no full text of the sourcecites [35] Levendusky, M. The microfoundations of mass polarization. Polit. Anal. 17, 162–176 (2009). source
• ?Not checked — no full text of the sourcecites [38] Levendusky, M. Clearer cues, more consistent voters: a benefit of elite polarization. Polit. Behav. 32, 111–131 (2010). source
• ?Not checked — no full text of the sourcecites [77] Park, B. How are we apart? Continuity and change in the structure of ideological disagreement in the American public, 1980–2012. Soc. Forces 96, 1757–1784 (2018). This article describes three types of ideological disagreement — polarization, partisan sorting and dimensional alignment — and analyses historical trends in US public opinion for each dimension. source

In the paper

“By exaggerating the prototypical characteristics of out-group members in these ways, ideologues increase the perceived social distance between different groups and might stereotype, discredit or marginalize the out-group.”

In the paper

“Some of these techniques (reducing anger and competition) might reduce ego-defensive motivation itself, whereas others (correcting misperceptions) seek to undo the consequences of ego-defensive processing.”

In the paper

“Whereas ego-justifying and group-justifying motives contribute to relatively symmetrical forms of polarization on the liberal-left and conservative-right, a third class of cognitive–motivational mechanisms related to system justification might contribute to ideological asymmetries99,149.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [99] Jost, J. T., Hennes, E. P. & Lavine, H. in The Oxford Handbook of Social Cognition (ed. Carlston, D. E.) 851–875 (Oxford Univ. Press, 2013).
• ?Not checked — no full text of the sourcecites [149] Eibach, R. Ideological polarization and social psychology. Oxford Res. Encyc. Psychol. https://doi.org/10.1093/acrefore/9780190236557.013.240 (2021). source

In the paper

“This is because system justification motivation — defined as the (not necessarily conscious) system-serving tendency to defend, bolster and legitimize aspects of the societal status quo — is generally correlated with political conservatism101.”

What the sources say

• ?Not checked — no full text of the sourcecites [101] Jost, J. T. A Theory of System Justification (Harvard Univ. Press, 2020). source

In the paper

“in game-theoretic terms, people who embrace liberal ideology are more likely than those who embrace conservative ideology to ‘cooperate’, whereas the latter are more likely to ‘defect’107.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [107] Jost, J. T. Left And Right: The Psychological Significance Of A Political Distinction (Oxford Univ. Press, 2021).

In the paper

“Descriptive social norms about what other people think or do and injunctive norms about what people ought to think or do are two major sources of social influence322.”

What the sources say

• ?Not checked — no full text of the sourcecites [322] Cialdini, R. B. & Jacobson, R. P. Influences of social norms on climate change-related behaviors. Curr. Opin. Behav. Sci. 42, 1–8 (2021). source

In the paper

“However, they differ in terms of system-justifying (versus system-challenging) motives, which might help to explain asymmetric polarization10,34,47,48,73,74.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [10] McCarty, N., Poole, K. T. & Rosenthal, H. Polarized America: the Dance of Ideology and Unequal Riches (MIT Press, 2016).
• ?Not checked — no full text of the sourcecites [34] Bonica, A. & Sen, M. Estimating judicial ideology. J. Econ. Perspect. 35, 97–118 (2021). source
• ?Not checked — no full text of the sourcecites [47] Lupton, R. N., Smallpage, S. M. & Enders, A. M. Values and political predispositions in the age of polarization: examining the relationship between partisanship and ideology in the United States, 1988–2012. Br. J. Polit. Sci. 50, 1–20 (2017). This study uses over-time data to show that alignment between ideology and partisanship has increased asymmetrically among those with conservative value orientations, presumably owing to Republican discourse emphasizing traditional family values and resistance to social change. source
• ?Not checked — no full text of the sourcecites [48] Webster, S. W. & Abramowitz, A. I. The ideological foundations of affective polarization in the US electorate. Am. Polit. Res. 45, 621–647 (2017). This article uses survey and experimental data to show that ideological beliefs (polarization) influence affective polarization, especially when it comes to social welfare issues. source
• ?Not checked — no full text of the sourcecites [73] Hacker, J. & Pierson, P. in Solutions to Political Polarization in America (ed. Persily, N.) 59–70 (Cambridge Univ. Press, 2015). source
• ?Not checked — no full text of the sourcecites [74] Grossmann, M. & Hopkins, D. A. Asymmetric Politics: Ideological Republicans and Group Interest Democrats (Oxford Univ. Press, 2016). source

In the paper

“Sources are more effective in influencing others when they are perceived as in-group members92 and as credible, trustworthy, powerful and/or attractive188.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [92] Van Bavel, J. J. & Packer, D. The Power of Us: Harnessing Our Shared Identities to Improve Performance, Increase Cooperation, and Promote Social Harmony (Little Brown Spark, 2021).
• ?Not checked — no full text of the sourcecites [188] McGuire, W. J. Constructing Social Psychology: Creative And Critical Processes (Cambridge Univ. Press, 1999). source

In the paper

“These and other studies327,328 highlight the ways in which norms tied to social contexts such as geographic locations influence political preferences and contribute to polarization329.”

What the sources say

• ?Not checked — no full text of the sourcecites [327] Perez-Truglia, R. & Cruces, G. Partisan interactions: evidence from a field experiment in the United States. J. Polit. Econ. 125, 1208–1243 (2017). source
• ?Not checked — no full text of the sourcecites [328] Perez-Truglia, R. Political conformity: event-study evidence from the United States. Rev. Econ. Stat. 100, 14–28 (2018). source
• ?Not checked — no full text of the sourcecites [329] Martin, G. J. & Webster, S. W. Does residential sorting explain geographic polarization? Polit. Sci. Res. Meth. 8, 215–231 (2020). source

In the paper

“Message framing has the potential to reduce polarization to the extent that it assuages ego- and group-justification motives by, for example, alleviating personal or collective insecurity, or taps into system-justification motives by appealing to patriotic traditions. However, some frames may increase polarization by eliciting ego- or group-defensiveness, accentuating categorical differences”

In the paper

“The latter style breeds political disengagement244, placing the fate of democracy in the hands of a small, non-representative subset of citizens.”

What the sources say

• ?Not checked — no full text of the sourcecites [244] Krupnikov, Y. & Ryan J. B. The Other Divide: Polarization And Disengagement In American Politics (Cambridge Univ. Press, 2022). source

In the paper

“Fourth, our psychological framework cannot easily explain historically changing levels of polarization or elites’ choice of communication strategies.”

In the paper

“Unfortunately, there are often political incentives for partisan elites to exploit the more polarizing strategies of message framing to maximize support and turnout among their staunchest constituents.”

In the paper

“It is, in principle, possible to layer structural and institutional variables onto our psychological framework, and this would facilitate comparative analysis of political polarization (Box 2).”

In the paper

“Whereas liberal-leftists are more willing to challenge the societal status quo and push for egalitarian forms of social change, conservative-rightists are more authoritarian and more protective of cultural traditions as well as longstanding social, economic and political institutions101,107,149,166,168,172.”

What the sources say

• ?Not checked — no full text of the sourcecites [101] Jost, J. T. A Theory of System Justification (Harvard Univ. Press, 2020). source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [107] Jost, J. T. Left And Right: The Psychological Significance Of A Political Distinction (Oxford Univ. Press, 2021).
• ?Not checked — no full text of the sourcecites [149] Eibach, R. Ideological polarization and social psychology. Oxford Res. Encyc. Psychol. https://doi.org/10.1093/acrefore/9780190236557.013.240 (2021). source
• ?Not checked — no full text of the sourcecites [166] Womick, J., Rothmund, T., Azevedo, F., King, L. A. & Jost, J. T. Group-based dominance and authoritarian aggression predict support for Donald Trump in the 2016 US presidential election. Soc. Psychol. Pers. Sci. 10, 643–652 (2019). source
• ?Not checked — no full text of the sourcecites [168] Nilsson, A. & Jost, J. T. The authoritarian-conservatism nexus. Curr. Opin. Behav. Sci. 34, 148–154 (2020). source
• ?Not checked — no full text of the sourcecites [172] Becker, J. C. Ideology and the promotion of social change. Curr. Opin. Behav. Sci. 34, 6–11 (2020). source