If smiles are so easy to fake, why do we trust them?

To better understand why we trust smiles, psychologists like me have turned to a branch of evolutionary biology called signalling theory for insight. This theory states that a communication signal between animals can remain ‘honest’ – ie, it can be trusted – if it’s effortful for the animal sending it. Consider the way that African springbok jump in the air (what’s called ‘pronking’) to indicate to predators that they’re young and fit, and that chasing them will therefore be too difficult. Jumping is effortful for the springbok, so they’re unlikely to bother with it unless they’re genuinely young and fit – making the signal more believable to predictors.

Something similar happens with human social interaction. …

By Alexander Danversis, University of Arizona for Psyche Magazine

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