Despite how little we actually know about yawning and why we do it, at least one thing's for certain: Yawning really is contagious. But maybe not for the reason most of us have come to believe.
Research has long supported the idea that yawning displays a person's capacity for empathy, and that the closer you are to a yawner, the greater the pull of their yawns. But a new study suggests empathy may not actually hold much sway.
In the new study, published in PLOS One, 328 participants were tested on a number of measures of cognition, emotion and fatigue before watching a three-minute yawning video. Of those 328, 222 yawned at least once during the video, and some yawned up to 15 times. Empathy, intelligence and even time of day showed no strong connections with the catching nature of these yawns; instead, the only factor that seemed to predict contagious yawning was age, according to the study.
More than 80 percent of people under 25 yawned contagiously, while 60 percent of 25 to 49 year olds did. And just 41 percent of people 50 or older yawned contagiously, the BBC reported, suggesting that yawns become less contagious as we age. However, other factors must be at work: Age only accounted for an 8 percent difference in yawn response, according to the study.
"Age was the most important predictor of contagious yawning, and even age was not that important," study author Elizabeth Cirulli, Ph.D., assistant professor of medicine at the Center for Human Genome Variation at Duke University School of Medicine, said in a statement. "The vast majority of variation in the contagious yawning response was just not explained."
Further research may help determine a genetic variant in people who yawn contagiously and those who don't, which may in turn help unearth more clues into diseases like autism or schizophrenia, she said.