Smiles Aren't Created Equally: Research Finds Physical Impacts Of Different Smiles


Different smiles have different meanings and now, researchers find just how differently the bodies physically react to smiles.

The results of the study show how intuitive people can be to non-verbal social evaluation.

3 Types Of Smile

Not all smiles are created with the intention of expressing joy. In fact, some of them aren't as positive in intention and emotion. A previous study made this point clear enough, where researchers determined three types of smile based on the muscle combinations used to make them.

The "reward" smile is the intuitive kind of smile, which reinforces behavior while the "affiliative" smile is made to maintain bonds, and the "dominance" smile is to claim a higher status in social hierarchies.

Building on the theory about the different kinds of smile, researchers of the new study focused on how such smiles would physically affect its recipients. As expected, they found that each of the smiles could elicit different physiological reactions.

Prerecorded Smiles

In order to gather their data, researchers asked 90 male college students to engage in impromptu speaking assignments, which would then be judged by a fellow student over a webcam. However, instead of being judged by a fellow student, each participant actually just saw a prerecorded version of a single type of smile.

All the while, researchers monitored the heart rates of the participants and collected saliva samples every so often to measure cortisol, a hormone that is associated with stress.

Feedback Perception

Researchers found that bodies of the participants actually reacted differently based on the type of smile they received. Specifically, dominant smiles were associated with high cortisol levels in the saliva and increased in heart rate perhaps because the participants took the smiles as negative feedback.

On the other hand, reward smiles appeared to have buffered the participants from stress and producing cortisol. Although affiliation smiles did not yield clear physical reactions, the results of which were much closer to the results of reward smiles.

"If they received dominance smiles, which they would interpret as negative and critical, they felt more stress, and their cortisol went up and stayed up longer after their speech. If they received reward smiles, they reacted to that as approval, and it kept them from feeling as much stress and producing as much cortisol," said Paula Niedenthal, co-author of the current study and of the previous study, which determined the types of smile.

Generally speaking, the results suggest that when delivered as evaluation feedback, the different types of a smile could result in physiological changes in the smile's recipient. As such, the subtle differences in an individual's smiles and facial expressions can essentially change the experience of the person they are talking to, suggesting a deep way wherein smiles can affect social interaction.

The study is published in the journal Scientific Reports.

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