The study demonstrated that people who have faced rejection have an enhanced ability to determine whether the "happy" face before them is genuine or not.
Led by Michael Bernstein, a Miami doctoral student in social psychology and one of the researchers, the study was conducted on 32 subjects, 17 women and 15 men.
The researchers found that the subjects who were manipulated to feel rejection could distinguish a fake smile from a real one nearly 80 percent of the time.
"This seems to be a skill we've acquired through evolution. Living in groups several hundreds of years ago was extremely important to survival. Being kicked out of the group was like death, so they became very good at reading facial expressions and social cues. People these days who are rejected are in a dangerous place because of evolutional pressure to find their way back into a group," said Bernstein
At the start of the study, some of the researchers thought the outcome would be just the opposite.
"Some thought the subjects who had been rejected would latch on to any sign of positivity and accept the insincere smiles as genuine. But it's clear we're equipped with radar for identifying who is open to affiliation and who is not," said Bernstein.
He speculated that real smiles are incredibly difficult to fake because a real smile is an automatic response to a positive feeling.
Further, he added that if you can tell the difference between a real and fake smile, you can identify a good person who you can relate with, and accordingly avoid the others.
The study was published in the latest issue of the journal Psychological Science.