IDEAS home Printed from
MyIDEAS: Log in (now much improved!) to save this paper

Learning in Society

  • Braz Camargo


    (Economics University of Western Ontario)

In the canonical learning model, the multi-armed bandit with independent arms, a decision maker learns about the different alternatives only through his private experience. It is well known that any optimal experimentation strategy for this problem is ex-post inefficient: it sometimes leads the superior alternative to be dropped altogether. Many situations of interest, however, involve learning from individual experience and the experience of others. This paper shows how learning in society can overcome this inefficiency. We consider an economy populated with a continuum of infinitely lived agents where each one of them faces a multi-armed bandit. The unknown stochastic payoffs of each arm are the same for all agents. In each period, they are randomly and anonymously matched in pairs, and in any such match they observe their partner's current action choice and its outcome. We establish that if initial beliefs are sufficiently heterogeneous, then the fraction of the population choosing the superior arm converges to one in any perfect bayesian equilibrium of this game. We also show that the same conclusion holds when only action choices are observable within a match and the number of arms is two

If you experience problems downloading a file, check if you have the proper application to view it first. In case of further problems read the IDEAS help page. Note that these files are not on the IDEAS site. Please be patient as the files may be large.

File URL:
Download Restriction: no

Paper provided by Society for Economic Dynamics in its series 2006 Meeting Papers with number 435.

in new window

Date of creation: 03 Dec 2006
Date of revision:
Handle: RePEc:red:sed006:435
Contact details of provider: Postal:
Society for Economic Dynamics Marina Azzimonti Department of Economics Stonybrook University 10 Nicolls Road Stonybrook NY 11790 USA

Web page:

More information through EDIRC

References listed on IDEAS
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:

as in new window
  1. Cripps, Martin William & Keller, R Godfrey & Rady, Sven, 2003. "Strategic Experimentation with Exponential Bandits," CEPR Discussion Papers 3814, C.E.P.R. Discussion Papers.
  2. James Peck & Huanxing Yang, 2011. "Investment Cycles, Strategic Delay, And Self‐Reversing Cascades," International Economic Review, Department of Economics, University of Pennsylvania and Osaka University Institute of Social and Economic Research Association, vol. 52(1), pages 259-280, 02.
  3. Juang, Wei-Torng, 2001. "Learning from Popularity," Econometrica, Econometric Society, vol. 69(3), pages 735-47, May.
  4. Smith, L. & Sorensen, P., 1996. "Pathological Outcomes of Observational Learning," Economics Papers 115, Economics Group, Nuffield College, University of Oxford.
  5. Gale, D. & Chamley, C., 1992. "Information Revelation and Strategic Delay in a Model of Investment," Papers 10, Boston University - Department of Economics.
  6. Venkatesh Bala & Sanjeev Goyal, 1998. "Learning from Neighbours," Review of Economic Studies, Oxford University Press, vol. 65(3), pages 595-621.
  7. Patrick Bolton & Christopher Harris, 1999. "Strategic Experimentation," Econometrica, Econometric Society, vol. 67(2), pages 349-374, March.
  8. Podczeck, Konrad & Puzzello, Daniela, 2009. "Independent Random Matching," MPRA Paper 27687, University Library of Munich, Germany, revised Sep 2010.
  9. Ellison, Glenn & Fudenberg, Drew, 1992. "Rules of Thumb for Social Learning," IDEI Working Papers 17, Institut d'Économie Industrielle (IDEI), Toulouse.
  10. Crimaldi, Irene & Pratelli, Luca, 2005. "Two inequalities for conditional expectations and convergence results for filters," Statistics & Probability Letters, Elsevier, vol. 74(2), pages 151-162, September.
  11. Banks, Jeffrey S & Sundaram, Rangarajan K, 1992. "Denumerable-Armed Bandits," Econometrica, Econometric Society, vol. 60(5), pages 1071-96, September.
  12. Banerjee, Abhijit & Fudenberg, Drew, 2004. "Word-of-mouth learning," Games and Economic Behavior, Elsevier, vol. 46(1), pages 1-22, January.
  13. Aoyagi, Masaki, 1998. "Mutual Observability and the Convergence of Actions in a Multi-Person Two-Armed Bandit Model," Journal of Economic Theory, Elsevier, vol. 82(2), pages 405-424, October.
  14. Bikhchandani, Sushil & Hirshleifer, David & Welch, Ivo, 1992. "A Theory of Fads, Fashion, Custom, and Cultural Change in Informational Cascades," Journal of Political Economy, University of Chicago Press, vol. 100(5), pages 992-1026, October.
  15. Caplin, Andrew & Leahy, John, 1994. "Business as Usual, Market Crashes, and Wisdom after the Fact," American Economic Review, American Economic Association, vol. 84(3), pages 548-65, June.
  16. Gale, Douglas & Kariv, Shachar, 2003. "Bayesian learning in social networks," Games and Economic Behavior, Elsevier, vol. 45(2), pages 329-346, November.
  17. Rosenberg, Dinah & Solan, Eilon & Vieille, Nicolas, 2009. "Informational externalities and emergence of consensus," Games and Economic Behavior, Elsevier, vol. 66(2), pages 979-994, July.
  18. Monica Brezzi & Tze Leung Lai, 2000. "Incomplete Learning from Endogenous Data in Dynamic Allocation," Econometrica, Econometric Society, vol. 68(6), pages 1511-1516, November.
  19. A. Banerjee & Drew Fudenberg, 2010. "Word-of-Mouth Communication and Social Learning," Levine's Working Paper Archive 425, David K. Levine.
  20. Dennis E. Smallwood & John Conlisk, 1979. "Product Quality in Markets Where Consumers are Imperfectly Informed," The Quarterly Journal of Economics, Oxford University Press, vol. 93(1), pages 1-23.
  21. Dinah Rosenberg & Eilon Solan & Nicolas Vieille, 2004. "Social Learning in One-Arm Bandit Problems," Discussion Papers 1396, Northwestern University, Center for Mathematical Studies in Economics and Management Science.
  22. Rothschild, Michael, 1974. "A two-armed bandit theory of market pricing," Journal of Economic Theory, Elsevier, vol. 9(2), pages 185-202, October.
  23. Easley, David & Kiefer, Nicholas M, 1988. "Controlling a Stochastic Process with Unknown Parameters," Econometrica, Econometric Society, vol. 56(5), pages 1045-64, September.
  24. Abhijit V. Banerjee, 1992. "A Simple Model of Herd Behavior," The Quarterly Journal of Economics, Oxford University Press, vol. 107(3), pages 797-817.
Full references (including those not matched with items on IDEAS)

This item is not listed on Wikipedia, on a reading list or among the top items on IDEAS.

When requesting a correction, please mention this item's handle: RePEc:red:sed006:435. See general information about how to correct material in RePEc.

For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (Christian Zimmermann)

If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

If references are entirely missing, you can add them using this form.

If the full references list an item that is present in RePEc, but the system did not link to it, you can help with this form.

If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your profile, as there may be some citations waiting for confirmation.

Please note that corrections may take a couple of weeks to filter through the various RePEc services.

This information is provided to you by IDEAS at the Research Division of the Federal Reserve Bank of St. Louis using RePEc data.