Friederike Mengel - Opinion Dynamics and Social Identity (ERC grant)

Opinion Dynamics

(ERC Grant 805017)

Under my ERC Starting grant "Opinion Dynamics" (2018-2023) I study how people form and revise beliefs about themselves and the world and how social identity affects this process. We study opinion dynamics in social networks, committees or other groups and ask when opinion dynamics lead to good outcomes and how they can derail to produce "collective delusions". Our research has shown among others that deliberation in committees can lead to an increase in gender bias, that social identity affects belief formation in a variety of contexts and that failures to update rationally could be behind a substantial share of observed discrimination. Social Identity can be both a boon and a bane for efficient information aggregation. On this site I periodically update about the activities and outcomes from the grant. Support from the ERC is gratefully acknowledged.

As the grant has finished this page now includes also other research on the topic of social identity and opinion dynamics that was not conducted under the ERC grant.

Publications:

Non Bayesian Statistical Discrimination (joint with Pol Campos Mercade), Management Science 70 (4) (2024), 2549-2567.

Abstract: Models of statistical discrimination typically assume that employers make rational inference from (education) signals. However, there is a large amount of evidence showing that most people do not update their beliefs rationally. We use a model and two experiments to show that employers who are conservative, in the sense of signal neglect, discriminate more against disadvantaged groups than Bayesian employers. We find that such irrational statistical discrimination deters high-ability workers from disadvantaged groups from pursuing education, further exacerbating initial group inequalities. Excess discrimination caused by employer conservatism is especially important when signals are very informative. Out of the overall hiring gap in our data, around 40% can be attributed to rational statistical discrimination, a further 40% is due to irrational statistical discrimination, and the remaining 20% is unexplained or potentially taste-based.

Gender Bias in Opinion Aggregation, International Economic Review 62(3) (2021), 1055-1080.

Abstract: Gender biases have been documented in areas including hiring, promotion or performance evaluations. Many of these decisions are made by committees. We experimentally investigate whether committee deliberation contributes to gender biases. In our experiments participants perform a real effort task with subjective performance and then rate the task performance of other participants. In a 3 x2 design we vary the extent to which communication among raters is possible and whether or not the experiment is gender-blind. There is substantial evidence of gender bias with open committee deliberation. In this case 60 percent of ratings received by men are revised upwards after deliberation compared to only 25 percent of ratings received by women. As a consequence women are ranked on average three positions lower after deliberation. We explore several mechanisms and test two interventions for open deliberation. Randomizing the order of speaking does not reduce gender bias, but an information intervention where raters are informed of gender bias in prior sessions does.

Gender Differences in Networking, Economic Journal, 130 (630) (2020), 1842-1873. [Replication Data]

Abstract: Gender differences in networking have been cited as an important reason behind gender earnings and promotion gaps. Despite this fact there is comparatively little evidence on whether such differences exist or what they look like. We conduct a series of experiments to gain insight into these questions. The experiments are designed to understand differences in the strategic use of networks, when both men and women have the same opportunities to network. While we do find evidence of gender earnings and promotion gaps in the lab, we do not find evidence of gender differences in network formation, except for the fact that men display more homophily than women. Women and men do, however, not systematically differ in terms of the number of links formed or received nor in terms of their centrality in the network. Earnings and promotion gaps appear partly because male decision makers are more likely to reward their (predominantly male) network neighbours with increased earnings as well as promotion.

Gender Bias in Teaching Evaluations, joint with J. Sauermann and U. Zoelitz, Journal of the European Economic Association 17(2) (2019), 535-566. [Online Appendix]

[Media: The Economist, Sueddeutsche Zeitung, Bayerischer Rundfunk, Times Higher Education, IZA Newsroom]
Abstract: This paper provides new evidence on gender bias in teaching evaluations. We exploit a quasi-experimental dataset of 19,952 student evaluations of university faculty in a context where students are randomly allocated to female or male instructors. Despite the fact that neither students’ grades nor self-study hours are affected by the instructor’s gender, we find that women receive systematically lower teaching evaluations than their male colleagues. This bias is driven by male students’ evaluations, is larger for mathematical courses, and particularly pronounced for junior women. The gender bias in teaching evaluations we document may have direct as well as indirect effects on the career progression of women by affecting junior women’s confidence and through the reallocation of instructor resources away from research and toward teaching. (JEL: J16, J71, I23, J45)

Identity,Homophily and In-Group Bias, joint with S. Currarini., European Economic Review 90 (SI: Social Identity and Discrimination) 2016, 40-55. [Replication Data]

Abstract: Many instances of social interaction display either or both of the following well-documented phenomena. People tend to interact with similar others (homophily). They also tend to treat others of shared social identity more favorably (in-group bias). While both phenomena involve some degree of discrimination towards others, a systematic study of their relations and interplay is yet missing. In this paper we report the findings of an experiment designed to address this issue. Participants are exogenously and randomly assigned to one of two groups. Subsequently they play a sequence of eight games with either an in-group or an out-group member. In treatment EXO in- and out-group matches are formed exogenously, while in ENDO participants can choose between in- and out-group matches. We find strong evidence of in-group bias in EXO, and strong evidence of homophily in ENDO. In-group biases, however, either decrease or disappear altogether under endogenous matching. We show that self-selection of homophilous agents into in-group matches cannot explain this fact. We also find that homophily is strongly correlated with risk aversion, and we build on this evidence to derive a rationale for both the existence of homophily and the disappearance of in-group biases under endogenous matching.

Literature Surveys:

Gender Differences in Networking - A Survey, prepared for EE Handbook on Experimental Economics of Gender (2024).
Learning in Social Networks , Chapter 82 in Elgar Encyclopedia of Behavioural and Experimental Economics, ed S-H Chuah, R. Hoffmann and A. Neelim, Cheltenham, UK: Edward Elgar Publishing, February 2025.

Presentations:

Gender Bias in Opinion Aggregation

presented at: WEHIA London, Amsterdam, Munich, Innsbruck, Lund, Nuremberg, Konstanz, King's College London, ASFEE Nice, Birmingham, NYU Abu Dhabi, Reading, Toulouse, Alicante (COSME special session), Newcastle Experimental Economics Workshop, MBEES 2022.

Non-Bayesian Statistical Discrimination (joint with Pol Campos Mercade)

presented at: Lund, Indiana University, Pittsburgh, IMT Lucca, Duke Kunshan University, WU Vienna, Gothenburg, Virginia Tech, HSE Moscow, BRIQ beliefs workshop Bonn, University of Hamburg, University of Alicante, GATE Lyon St Etienne, IAST University of Toulouse, Berlin Behavioural Seminar, University of Glasgow, Uppsala University, Queen Mary University London; IWET Workshop Chile, University College London, University of Duesseldorf, British Academy Conference on Cohesive Societies, University of Bologna.
[Link to Video of presentation at IWET]

Diversity in Committees (joint with N. Hughes and Z. UH Khan)

presented at: University of Manchester, Lund University, University of Dublin, University of Surrey, University of Southhampton, University of Exeter, Universidad de las Islas Baleares, POLECON UK 2023, Ludwig Maximilians University Munich.

Match Length Realization and cooperation in indefinitely repeated games (joint with L. Orlandi and S. Weidenholzer)

presented at: University of Heidelberg, Lund University, University of East Anglia, University of Southampton, VIBES, Oxford University, University of California Davis.

Conference

The interdisciplinary workshop at the University of Essex on Inequality, Identity and Beliefs had to be cancelled due to Covid.

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