The Value of a Smile: Game Theory with a Human Face

24 Pages Posted: 18 May 2011

See all articles by Catherine C. Eckel

Catherine C. Eckel

Texas A&M University

Rick K. Wilson

Rice University - Department of Political Science

Jorn Scharlemann

University of Sussex

Alex Kacelnik

University of Oxford

Date Written: February 1, 2001


Many economists and biologists view cooperation as anomalous: animals (including humans) that pursue their own self-interest have superior survival odds to their altruistic or cooperative neighbors. However, in many situations there are substantial gains to the group that can achieve cooperation among its members, and to individuals who are members of those groups. For an individual, the key to successful cooperation is the ability to identify cooperative partners. The ability to signal and detect the intention to cooperate would be a very valuable skill for humans to posses.

Smiling is frequently observed in social interactions between humans, and may be used as a signal of the intention to cooperate. However, given that humans have the ability to smile falsely, the ability to detect intentions may go far beyond the ability to recognize a smile. In the present study, we examine the value of a smile in a simple bargaining context. 120 subjects participate in a laboratory experiment consisting of a simple two-person, one-shot “trust” game with monetary payoffs. Each subject is shown a photograph of his partner prior to the game; the photograph is taken from a collection that includes one smiling and one non-smiling image for each of 60 individuals. These photographs are also rated by a separate set of subjects who complete a semantic differential survey on affective and behavioral interpretations of the images.

Results lend some support to the prediction that smiles can elicit cooperation among strangers in a one-shot interaction. Other characteristics of faces also appear to elicit cooperation. Factor analysis of the survey data reveals an important factor, termed “cooperation”, which is strongly related to trusting behavior in the game. This factor is correlated with smiling, but is somewhat more strongly predictive of behavior than a smile alone. In addition, males are found to be more cooperative, especially towards female images, whereas females are least cooperative towards female images.

Keywords: Trust, Behavioral Game Theory, Facial Expressions, Sex Differences

JEL Classification: C7, C91

Suggested Citation

Eckel, Catherine C. and Wilson, Rick K. and Scharlemann, Jorn Peter and Kacelnik, Alex, The Value of a Smile: Game Theory with a Human Face (February 1, 2001). Journal of Economic Psychology, Vol. 22, 2001, Available at SSRN:

Catherine C. Eckel (Contact Author)

Texas A&M University ( email )

5201 University Blvd.
College Station, TX 77843-4228
United States

Rick K. Wilson

Rice University - Department of Political Science ( email )

Houston, TX 77005-1892
United States

Jorn Peter Scharlemann

University of Sussex

School of Life Sciences
Brighton, Sussex BN1 9QG
United Kingdom

Alex Kacelnik

University of Oxford ( email )

Mansfield Road
Oxford, Oxfordshire OX1 4AU
United Kingdom

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