A new research has suggested that a person's ability to yawn after seeing another person do the same reduces with age.
The study from the Duke Center for Human Genome Variation is the most comprehensive look at factors influencing contagious yawning to date.
Study author Elizabeth Cirulli said that the lack of association in the study between contagious yawning and empathy suggests that contagious yawning is not simply a product of one's capacity for empathy.
Previous research, including neuroimaging studies, has shown a relationship between contagious yawning and empathy, or the ability to recognize or understand another's emotions. Other studies have shown correlations between contagious yawning and intelligence or time of day.
The current study aimed to better define how certain factors affect someone's susceptibility to contagious yawning.
The researchers recruited 328 healthy volunteers, who completed cognitive testing, a demographic survey, and a comprehensive questionnaire that included measures of empathy, energy levels and sleepiness.
The participants then watched a three-minute video of people yawning, and recorded the number of times they yawned while watching the video.
The researchers found that certain individuals were less susceptible to contagious yawns than others, with participants yawning between 0 and 15 times during the video.
Of the 328 people studied, 222 contagiously yawned at least once. When verified across multiple testing sessions, the number of yawns was consistent, demonstrating that contagious yawning is a very stable trait.
In contrast to previous studies, the researchers did not find a strong connection between contagious yawning and empathy, intelligence or time of day.
The only independent factor that significantly influenced contagious yawning was age: as age increased, participants were less likely to yawn. However, age was only able to explain 8 percent of the variability in the contagious yawn response.
Cirulli said that age was the most important predictor of contagious yawning, but the vast majority of variation in the contagious yawning response was just not explained.
Because most variability in contagious yawning remains unexplained, the researchers are now looking to see whether there are genetic influences that contribute to contagious yawning.
The study is published in the journal PLOS ONE.
