Children as young as six can tell when you're faking a smile

Whether it's the awkward coincidence of meeting your boss in the supermarket aisle or a humourless joke by a new date, what would we do without the fake smile? It's not that the fake is all that convincing. Apparently most adults can tell the difference - the lopsidedness of the mouth and lack of creasing around the eyes gives it away. But the fact that the faker is trying their best to send a positive signal somehow saves face all round. Well, most of the time anyway.

Of course when you're dealing with a child you'd probably like to think you can pull a fake smile and they won't realise. 'Yes darling, that's a beautiful drawing' - big smile, encouraging voice. Indeed, past research suggested children can't tell a fake smile from a genuine one until about the age of nine or ten. But now a new study with a different methodology suggests that estimate may have to be brought forward to age six.

Pierre Gosselin's team at the University of Ottawa and Laurentian University devised a simpler paradigm than used previously. Sixty boys and girls aged six to seven and nine to ten watched pairs of videos of actors pulling either: a genuine smile (symmetrical, eyes creased); a lop-sided fake (eyes creased but asymmetrical intensity); or a mouth-only smile (symmetrical, no eye creasing). Each pair contained either two smiles of the same type or two different types. The children's task was to say whether the smiles were the same type or not.

Their accuracy wasn't great (around 60 per cent) but it was high enough to show that, based on either creasing around the eyes or symmetry, the kids were able to tell the difference between the smile types better than if they had simply been guessing. The younger children were also just as accurate as the older children.

Telling the different types of smile apart visually is only half the job. A second study tested whether another batch of children could read the appropriate meaning into the different smiles. The stimuli were the same as before but this time children successfully identified that the faces with genuine smiles were happier than those with lopsided or mouth-only smiles. At around 60 per cent, accuracy once again wasn't brilliant but was better than if they'd been guessing. This time, performance was better among the older children thus suggesting, as you'd expect, that detecting fake smiles is a skill that improves with age.

'The fact that six- and seven-year-old children are sensitive to the asymmetry of smiles and Cheek Raiser activity [creasing around the eyes] suggests they already have a significant amount of experience with social influence, and particularly with the use of smiles in social interactions,' the researchers said.
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Gosselin, P., Perron, M., & Maassarani, R. (2009). Children's ability to distinguish between enjoyment and non-enjoyment smiles. Infant and Child Development DOI: 10.1002/icd.648