According to a new research, people actually anticipate smiles that are genuine but not smiles that are merely polite.
The differing responses may reflect the unique social value of genuine smiles.
"These findings give us the first clear suggestion that the basic processes that guide responses to reward also play a role in guiding social behavior on a moment-to-moment basis during interactions," explained psychological scientist and lead researcher Erin Heerey of Bangor University (UK).
"No two interactions are alike, yet people still manage to smoothly coordinate their speech and nonverbal behaviors with those of another person," said Heerey.
She wondered whether the intrinsic value of different social cues like smiles might play a role in shaping our response to those cues.
Polite smiles, for example, typically occur when sociocultural norms dictate that smiling is appropriate. Genuine smiles, on the other hand, signify pleasure, occur spontaneously, and are indicated by engagement of specific muscles around the eye.
If genuine smiles are a form of social reward, Heerey hypothesized, people should be more likely to anticipate genuine smiles than relatively less rewarding polite smiles.
An observational study showed that pairs of strangers getting to know one another not only exchanged smiles, they almost always matched the particular smile type, whether genuine or polite.
But, they responded much more quickly to their partners' genuine smiles than their polite smiles, suggesting that they were anticipating the genuine smiles.
Similarly, participants in a lab-based study learned key-press associations for genuinely smiling faces faster than those for politely smiling faces. Data from electrical sensors on participants' faces revealed that they engaged smile-related muscles when they expected a genuine smile to appear but showed no such activity when expecting polite smiles.
The different responses suggest that genuine smiles are more valuable social rewards. Previous research shows that genuine smiles promote positive social interactions, so learning to anticipate them is likely to be a critical social skill.
Heerey concluded "As we progress in our understanding of how social interactions unfold, these findings may help to guide the development of interventions for people who find social interactions difficult, such as those with social anxiety, autism, or schizophrenia."
The new research is reported in Psychological Science, a journal of the Association for Psychological Science.