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How social information can improve estimation accuracy in human groups

  1. Guy Theraulazb,e,1
  1. aLaboratoire de Physique Théorique, CNRS, Université de Toulouse (Paul Sabatier), 31062 Toulouse, France;
  2. bCentre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, CNRS, Université de Toulouse, 31062 Toulouse, France;
  3. cDepartment of Behavioral Science, Hokkaido University, 060-0810 Sapporo, Japan;
  4. dToulouse School of Economics, Institut National de la Recherche Agronomique (INRA), Université de Toulouse (Capitole), 31000 Toulouse, France;
  5. eInstitute for Advanced Study in Toulouse, 31015 Toulouse, France;
  6. fToulouse School of Economics, Université de Toulouse (Capitole), 31000 Toulouse, France;
  7. gDepartment of Social Psychology, The University of Tokyo, 113-0033 Tokyo, Japan
  1. Edited by Burton H. Singer, University of Florida, Gainesville, FL, and approved October 2, 2017 (received for review March 5, 2017)


Digital technologies deeply impact the way that people interact. Therefore, it is crucial to understand how social influence affects individual and collective decision-making. We performed experiments where subjects had to answer questions and then revise their opinion after knowing the average opinion of some previous participants. Moreover, unbeknownst to the subjects, we added a controlled number of virtual participants always giving the true answer, thus precisely controlling social information. Our experiments and data-driven model show how social influence can help a group of individuals collectively improve its performance and accuracy in estimation tasks depending on the quality and quantity of information provided. Our model also shows how giving slightly incorrect information could drive the group to a better performance.


In our digital and connected societies, the development of social networks, online shopping, and reputation systems raises the questions of how individuals use social information and how it affects their decisions. We report experiments performed in France and Japan, in which subjects could update their estimates after having received information from other subjects. We measure and model the impact of this social information at individual and collective scales. We observe and justify that, when individuals have little prior knowledge about a quantity, the distribution of the logarithm of their estimates is close to a Cauchy distribution. We find that social influence helps the group improve its properly defined collective accuracy. We quantify the improvement of the group estimation when additional controlled and reliable information is provided, unbeknownst to the subjects. We show that subjects’ sensitivity to social influence permits us to define five robust behavioral traits and increases with the difference between personal and group estimates. We then use our data to build and calibrate a model of collective estimation to analyze the impact on the group performance of the quantity and quality of information received by individuals. The model quantitatively reproduces the distributions of estimates and the improvement of collective performance and accuracy observed in our experiments. Finally, our model predicts that providing a moderate amount of incorrect information to individuals can counterbalance the human cognitive bias to systematically underestimate quantities and thereby improve collective performance.


  • ?1To whom correspondence should be addressed. Email: guy.theraulaz{at}univ-tlse3.fr.
  • Author contributions: B.J., C.S., and G.T. designed research; B.J., H.-r.K., R.E., S.C., A.B., T.K., C.S., and G.T. performed research; B.J., C.S., and G.T. analyzed data; and B.J., C.S., and G.T. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1703695114/-/DCSupplemental.

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