Costly Signals, and the Paradox of Rationality: Smiles Edition

Marc Mehu, Karl Grammer & Robin Dunbar
Evolution and Human Behavior, forthcoming

Abstract:
One of the proposed functions of human smiling is to advertise cooperative
dispositions and thereby increase the likelihood that a social partner would
invest resources in a relationship. In particular, smiles involving an
emotional component would be honest signals of altruistic dispositions
because they are not easy to produce voluntarily. In this study, 60 people
were covertly filmed while interacting with a friend in two conditions:
control and sharing. Smiles were classified into Duchenne (spontaneous) and
non-Duchenne smiles. Participants also completed a series of questionnaires,
including the Altruism Scale and a self-report questionnaire of emotional
state. Interestingly, Duchenne smiles were displayed at higher rates in the
sharing situation as opposed to the control situation, whereas non-Duchenne
smiles were unaffected by the type of interaction. Furthermore, Duchenne
smiles in the sharing interaction were positively affected by a measure of
altruism. Self-reported emotional states did not vary between conditions and
were poorly related to smiling. This study shows that the Duchenne smile is
relevant to situations that involve the sharing of material resources
because it would reliably advertise altruistic intentions. The Duchenne
smile could therefore be an important signal in the formation and
maintenance of cooperative relationships.

A number of people have claimed that the reason humans got big brains was the advantages conferred in terms of detecting dissembling.

So....a big fake smile does you no good.

But a big real smile means you are altruistic, and (paradoxically) people are more willing to give YOU stuff.

That means you should learn how to smile in a way people can't detect as fake.

But that means that other people want to be able to detect tiny cues, and body language, that mean you are faking.

Angus and I solve this problem by never smiling. Nobody can call US fakers.
Grrrrrr......

(Nod to KL, who never fakes it, either)