Persuading with Anecdotes

42 Pages Posted: 12 Apr 2021 Last revised: 25 Apr 2021

See all articles by Nika Haghtalab

Nika Haghtalab

University of California, Berkeley

Nicole Immorlica

Microsoft Research

Brendan Lucier

Microsoft Research

Markus M. Mobius

Microsoft Corporation - Microsoft Research New England; University of Michigan at Ann Arbor - School of Information; National Bureau of Economic Research (NBER)

Divyarthi Mohan

Princeton University

Date Written: April 2021

Abstract

We study a model of social learning and communication using hard anecdotal evidence. There are two Bayesian agents (a sender and a receiver) who wish to communicate. The receiver must take an action whose payoff depends on their personal preferences and an unknown state of the world. The sender has access to a collection of n samples correlated with the state of the world, which we think of as specific anecdotes or pieces of evidence, and can send exactly one of these samples to the receiver in order to influence her choice of action. Importantly, the sender's personal preferences may differ from the receiver's, which affects the seller's strategic choice of which anecdote to send. We show that if the sender's communication scheme is observable to the receiver (that is, the choice of which anecdote to send given the set they receive), then they will choose an unbiased and maximally informative communication scheme, no matter the difference in preferences. Without observability, however, even a small difference in preferences can lead to a significant bias in the choice of anecdote, which the receiver must then account for. This can significantly reduce the informativeness of the signal, leading to substantial utility loss for both sides. One implication is informational homophily: a receiver can rationally prefer to obtain information from a poorly-informed sender with aligned preferences, rather than a knowledgeable expert whose preferences may differ from her own.

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Suggested Citation

Haghtalab, Nika and Immorlica, Nicole and Lucier, Brendan and Mobius, Markus M. and Mohan, Divyarthi, Persuading with Anecdotes (April 2021). NBER Working Paper No. w28661, Available at SSRN: https://ssrn.com/abstract=3824538

Nika Haghtalab (Contact Author)

University of California, Berkeley ( email )

310 Barrows Hall
Berkeley, CA 94720
United States

Nicole Immorlica

Microsoft Research ( email )

One Memorial Drive, 14th Floor
Cambridge, MA 02142
United States

Brendan Lucier

Microsoft Research ( email )

One Memorial Drive, 14th Floor
Cambridge, MA 02142
United States

Markus M. Mobius

Microsoft Corporation - Microsoft Research New England ( email )

One Memorial Drive, 12th Floor
Office 12062
Cambridge, MA 02142
United States

HOME PAGE: http://www.markusmobius.org

University of Michigan at Ann Arbor - School of Information ( email )

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550 East University
Ann Arbor, MI 48109-1092
United States

HOME PAGE: http://www.markusmobius.org

National Bureau of Economic Research (NBER) ( email )

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Cambridge, MA 02138
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HOME PAGE: http://www.markusmobius.org

Divyarthi Mohan

Princeton University

22 Chambers Street
Princeton, NJ 08544-0708
United States

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