Smiling as a costly signal

Costly signaling has been extensively studied both in economics since the work of Spence (1974), and independently in biology since the work of Zahavi(1975). A signal is any observable trait that imposes a cost on its bearer (a pecuniary or non-pecuniary effort cost in economics, a fitness cost in biology) but which reliably indicates the presence of some advantageous hidden trait because the signal is more costly for those individuals that do not possess the trait than for those who do.The benefit from signaling the hidden trait is that it attracts partners in mating or in some other mutually beneficial cooperative activity, and the benefit to the signaler of doing so must exceed the cost of the signal.


Inspired by results from affective sciences that
emotions are not just some random noise but an essential part of the decision making mechanism (Damasio, 1994), theoretical and experimental work has turned to
investigate the effect of different emotions and other visceral factors on decision
making.


Smiles are on the one hand an expression of experienced happiness and might be used as a coordination device (Manzini et al 2009), but smiling is also an important component in social exchange (Owen & Bacharowski, 2001).


The results show that smiling pictures are more often trusted than their non-smiling counterpart.


However to be reliable, these signals must be costly and therefore difficult to mimic.