The three types of smile are: the reward smile, the affiliative smile and the dominance smile.
The reward smile, shown below on the left, is the type people use when they are happy.
The affiliative smile, shown in the middle below, is used to show we are friendly and not a threat.
The dominance smile, on the right, is closer to a sneer, but is linked to enjoying one’s higher status.
Professor Paula Niedenthal, who led the study, said:
“When distinguishing among smiles, both scientists and laypeople have tended to focus on true and false smiles.
The belief is that if you smile when you’re not happy, the smile is false.
But people smile in many different circumstances and during many emotional states.
So asserting that only smiles that result from states of happiness are ‘true’ smiles limits our understanding of this important facial expression.”
Professor Niedenthal explained the evolution of the smile:
“This facial expression has evolved to solve basic tasks of human living in social groups: Thanks, I like this.
Don’t worry, I’m not going to hurt you.
Hey, I’m in charge here.
There are so many words people use to describe different smiles, but we see them as describing subtypes of a reward situation or an affiliative situation or a situation of negotiating hierarchy and having disdain for someone else.”
Ms Rychlowska said:
“We now know which movements we should look for when we describe smiles from real life.
We can treat smiles as a set of mathematical parameters, create models of people using different types of smiles, and use them in new studies.”
Professor Niedenthal said:
“Americans smile so much that people from other countries are taught to smile more when they interact with us.
The problem is, they’re almost always taught one kind of smile, and that can cause confusion.
Simply teaching people about the existence of different types of ‘true’ smiles can help people pay more attention and avoid some of those misunderstandings.”
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The study was published in the journal Psychological Science (Rychlowska et al., 2017).