 Cooperation among non-kin evolved as a result of cooperators giving honest signals.  One such signal is involuntary facial expressions displaying positive emotions such as the “Duchenne” smiles.  Altruistic individuals display higher levels of positive emotion than non-cooperators.  Duchenne smiles correlate with altruistic tendencies only in situations requiring cooperation.

 Emotional expressivity can serve as a marker for an individual’s cooperative disposition.  Emotional expressivity makes it easier for cooperative individuals identified and chosen as interaction partners. Cooperators

 Duchenne smiles are sometimes unrelated to altruistic tendencies.  Duchenne smiles have been observed when individuals defeat an opponent.  The situation in which emotions are displayed may determine the degree to which they reflect cooperative disposition. Duchenne smile

 “We predict that cooperators, defined as those who make fair (i.e., 50-50) resource distributions as the proposer in the ultimatum game, would display higher levels of both positive and negative emotion than non-cooperators when they face unfair offers as the responder.”

 Displaying the correct emotion, both positive and negative would require mental effort, more than displaying positive emotion overall.  Individuals who honestly reveal their intentions to potential partners using involuntary signals of emotion such as facial expressions, blushing, or perspiration must commit to behaving in a cooperative manner,

 Twenty male participants recruited from a research university in Japan with the promise of money.  Participant’s cooperation was measured as they played the ultimatum game.  The ultimatum game allows measurement not only displays of the negative expressions of emotions of both the proposer and the responder, but also their behavioral tendency to cooperate.

 Pro-social are those who care about their partner’s welfare.  Pro-selfs are those who do not care about partner’s welfare.  This measure is used to qualify behavior of cooperativeness (fair offers as the proposer ) › Identify true cooperators as opposed to a prudent egoist who anticipates punishment for an unfair offer.

 Participants escorted individually into sound proof rooms – did not meet, see, or interact with each other.  Played truncated ultimatum game via computer with computer generated responses for the first 2 games.  1 st game – intentional unfair proposal game  2 nd game – non-intentional unfair proposal game  3 rd game – used to identify cooperators

 Each game had three phases pre-game, response phase, and post game phase.  Response phase was the focus of the study.  Video-taped the game players.  Coders scored emotional signals of the face associated with eight emotional categories; › anger, disgust, fear, sadness, contempt (negative) › Duchenne smile (positive) › non-Duchenne smile, and surprise (neutral)

 Marginal finding for whether or not they were cooperative or non-cooperative F1,18=3.48, p=.08, ηp 2 =.16,  Emotional valence was also found to be significant F2,36=8.56, p=.001, ηp 2 =.32  Interaction between proposer type and game phase F2,36=5.62, p=.01, ηp 2 =.23  These findings support the idea that cooperators show more overall emotion (positive, neutral, and negative) than do non-cooperators…in regards to a negative situation › there was an overall lack of proposer type and emotional valence interaction

 8 out of 11 behavioral cooperators were matched with being pro-social  8 out of 9 behavioral non-cooperators were classified as pro-selves

 The reason cooperators have been found to express more positive emotion may be due to their overall increased expressivity of emotion  More important for the valence of the emotion to establish whether the individual is pro-self or pro-social

 3 rationales for emotional expressivity as a reliable signal of cooperation › Both negative and positive emotions are difficult to fake › The task of faking emotions becomes much more formidable when positive and negative emotions must be displayed according to pro-social standards › Cost of displaying true emotion would be greater for a pro-self, thereby making them more likely to display less emotion overall

 Not very generalizable › It has been shown that emotional reactivity is different in women than in men › Culture would also play a large role in emotional expressivity › The participants were only interacting with a computer, and unbeknownst to them a computer was making the proposals for the first two games