Reinforcement generates systematic differences without heterogeneity

Alexandros Gelastopoulos, Lucas Sage and Arnout van de Rijt
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Alexandros Gelastopoulos: TSE-R - Toulouse School of Economics - UT Capitole - Université Toulouse Capitole - UT - Université de Toulouse - EHESS - École des hautes études en sciences sociales - CNRS - Centre National de la Recherche Scientifique - INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement
Lucas Sage: Economics Department [European University Institute] - EUI - European University Institute - Institut Universitaire Européen, CNR - National Research Council of Italy | Consiglio Nazionale delle Ricerche
Arnout van de Rijt: EUI - European University Institute - Institut Universitaire Européen

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Abstract: Inequality in outcomes may emerge through a reinforcement process in which stochastic variation in values is determined by prior values but may also originate in preexisting differences in unobserved factors. A common approach toward differentiating between these origins in longitudinal data is to attribute systematic differences between units—differences in means or differences proportional to a time-varying group average—to unobserved heterogeneity. We show that any longitudinal data with systematic differences can also be produced by a reinforcement-driven data generating process. This result reconciles findings in three distinct research areas—science of science, personal culture, and sexual networks—where reinforcement is a strong theoretical prior, yet longitudinal data analyses advance an explanation of interpersonal differences based on heterogeneity. Future studies may bound the role of heterogeneity and reinforcement from below by measuring fixed traits that systematically vary with the outcome and isolating random events that trigger emergent differences.

Date: 2025-06
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Published in Proceedings of the National Academy of Sciences of the United States of America, 2025, 122 (23), pp.e2408163122. ⟨10.1073/pnas.2408163122⟩

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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-05116133

DOI: 10.1073/pnas.2408163122

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