title: Reach and speed of judgment propagation in the laboratory.
abstract: In recent years, a large body of research has demonstrated that judgments and behaviors can propagate from person to person. Phenomena as diverse as political mobilization, health practices, altruism, and emotional states exhibit similar dynamics of social contagion. The precise mechanisms of judgment propagation are not well understood, however, because it is difficult to control for confounding factors such as homophily or dynamic network structures. We introduce an experimental design that renders possible the stringent study of judgment propagation. In this design, experimental chains of individuals can revise their initial judgment in a visual perception task after observing a predecessor's judgment. The positioning of a very good performer at the top of a chain created a performance gap, which triggered waves of judgment propagation down the chain. We evaluated the dynamics of judgment propagation experimentally. Despite strong social influence within pairs of individuals, the reach of judgment propagation across a chain rarely exceeded a social distance of three to four degrees of separation. Furthermore, computer simulations showed that the speed of judgment propagation decayed exponentially with the social distance from the source. We show that information distortion and the overweighting of other people's errors are two individual-level mechanisms hindering judgment propagation at the scale of the chain. Our results contribute to the understanding of social-contagion processes, and our experimental method offers numerous new opportunities to study judgment propagation in the laboratory.
authors.affiliation: Center for Adaptive Rationality, Max Planck Institute for Human Development, 14195 Berlin, Germany; moussaid@mpib-berlin.mpg.de.
authors.forename: Mehdi
authors.identifier: 0000-0002-1268-6332
authors.initials: M
authors.lastname: Moussaïd
authors.affiliation: Center for Adaptive Rationality, Max Planck Institute for Human Development, 14195 Berlin, Germany.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Herzog
authors.affiliation: Center for Adaptive Rationality, Max Planck Institute for Human Development, 14195 Berlin, Germany.|AG Progress Test Medizin, Charité Medical School, 10115 Berlin, Germany.
authors.forename: Juliane E
authors.initials: JE
authors.lastname: Kämmer
authors.affiliation: Center for Adaptive Rationality, Max Planck Institute for Human Development, 14195 Berlin, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Hertwig
mesh_terms: D004644:Emotions / Q000502:physiology*; D005260:Female; D006801:Humans; D007398:Interpersonal Relations; D007600:Judgment / Q000502:physiology*; D008297:Male; D012929:Psychological Distance; D012938:Social Perception
keywords: collective behavior; diffusion chains; information diffusion; social contagion; social influence