People smile for a variety of reasons and during different emotional states, not just happiness. But does this mean that non-happy smiles are false smiles?
In a new study, researchers crack the code of three widely-used social smiles and explain why these can be considered “true” smiles even though they don’t necessarily reflect happiness.
“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,” said Dr. Paula Niedenthal, a psychology professor at the University of Wisconsin-Madison.
“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.”
In the journal Psychological Science, U.K. researchers from Cardiff University and the University of Glasgow published a set of experiments that seek to expand our understanding of the human smile. They described three distinct, reliably recognizable expressions — smiles of reward, affiliation, and dominance — and identified the facial muscle combinations that make them.
Each smile relies on an anatomical feature known as the zygomaticus major, straps of facial muscle below the cheekbones that pull up the corners of the mouth. But this is not the only smile-related muscle.
For the study, participants viewed thousands of computer-generated expressions with random combinations of facial muscles activated, but always with the zygomaticus.
“We varied everything that could be varied in an expression, but our stimuli included some action from the smile muscle, the zygomaticus,” said Dr. Magdalena Rychlowska, a postdoctoral researcher at Cardiff.
“We asked participants to tell us when they see a reward or affiliative or a dominance smile, and when the expression is not a smile.”
Then the researchers showed these participant-sorted smiles to two more sets of volunteers, so that they eventually had recipes for each smile.
For example, a reward smile — “probably the most intuitive,” Niedenthal says, “the kind of smile you would use with a baby, so he will smile back or do things you like” — is a symmetrical pulling of zygomaticus muscles plus a slight eyebrow lift and some sharp lip pulling.
Affiliative smiles — used to communicate tolerance, acknowledgment, or a bond, and show that you’re not a threat — come with a similar symmetrical upturn to the mouth, but spread wider and thinner with pressed lips and no exposed teeth.
Dominance smiles are used to signify status and manage social hierarchies. They show symmetry, and include a slight lopsided sneer with the raised brows and lifted cheeks typically associated with expressing enjoyment.
“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,” Niedenthal said.
“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.”
Using these specific physical descriptions of smile types, researchers can better classify subtypes and study the use and effects of smiles in important social interactions.
“We now know which movements we should look for when we describe smiles from real life,” said Rychlowska. “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.”
The researchers are already investigating how affiliative and dominance smiles can shift the outcome of games and negotiations. Niedenthal is also working with surgeons who repair and reconstruct facial bones and muscles.
“They may have to make choices that will affect a patient’s expression for the rest of their life,” Niedenthal said. “It’s useful for them to know how different kinds of smiles are used in the world, and which muscles are involved in making them.”
More exact definitions of smile types may also help people navigate intercultural communication. Prior research has shown Niedenthal that while the types of smiles used vary from country to country, there is plenty of variation in how often they are used.
“Americans smile so much that people from other countries are taught to smile more when they interact with us,” she said. “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.”
Source: University of Wisconsin-Madison