If your partner does not yawn back quickly, there could be problems ahead, a team of Swedish researchers claim.
Researchers from Lund University in Sweden did the latest study at Tacugama Chimpanzee Sanctuary in Sierra Leone in west Africa.
The scientists noticed that yawns move more quickly from senders to catchers when relationships are close.
The phenomenon was least common among strangers.
According to them, a reciprocal yawn was most likely to occur among family members, then friends and then acquaintances.
"A yawn can reveal true love as humans do not pick up contagious yawning until age 4 or 5," science writer Sam Kean was quoted as saying in a Daily Mail report.
Those susceptible to contagious yawning are better at understanding what others are thinking from their faces.