If you see or hear somebody else yawn, or even think or read about yawning, there’s a good chance that you may yourself yawn; between 40 and 60 percent of people are susceptible to contagious yawning. Previous studies (for example here and here) suggest that contagious yawning has to do with how much empathy a person generally feels, and links have been drawn to a person’s intelligence, the time of day, and the weather.
But a new study found that none of those things matter nearly as much as your age, and whether or not you are susceptible to yawning in the first place. The study, published in PLOS ONE, found that almost all the people who contagiously yawned (after watching a video of people yawning) again yawned when tested at a later date, or in a different location. And the younger the person, the more likely they are to contagiously yawn.
Why might age be so important? Possible explanations “could include decreased attention to the stimulus with age, a reduced connection to the yawners in the video due to use of technology, or a general decline in susceptibility to contagious yawning as we age.”
The lack of connection between contagious yawning and measures of empathy (or intelligence, time of day and the like) conflicts with previous research, which involved fewer participants. These authors suggest that contagious yawning is a stable personality trait, which varies for unknown reasons, but may well be of genetic origin.
Researchers studied 328 participants, giving them cognitive tests and measuring their capacity for empathy. They then had the participants self-report how many times they yawned, which they wrote was the preferred way to take count; if people are aware they are being watched, it can prevent them from yawning.