Women are more likely to "catch" a yawn than men, according to new research from the University of Pisa in Italy.
The research findings, which were published in Royal Society Open Science, suggest there is growing evidence that infectious yawning might be an empathy-based phenomenon.
Researchers put forward the case that women have higher rates of "catching" a yawn because they are more empathetic than men. Psychological, clinical and neurobiological findings indicate empathic abilities are more developed in women than in men, the researchers said.
Subjects, who were unaware they were part of the study, were observed going about their daily lives over a five-year period. Researchers recorded their yawn responses within a three-minute observation window.
Author Dr Elisabetta Palagi said the new results confirmed a previous study that showed women were more likely to catch others' yawns compared to their male counterparts.
"Many other disciplines underlined the higher empathic abilities of women compared to men. The gender bias we found is extremely important because it clearly means that a linkage between yawn contagion and empathy is present," she said.
"In the first study we considered all the people, both susceptible and not susceptible, to respond to others' yawns. There were some people who never respond to others' yawns."
A wide range of sensory modes can cause a person to yawn, ranging from hearing, seeing, reading about or even thinking about yawning. It can be affected by different variables, like the time of day, a person's age, or familiarity between people.
The paper also said yawning was especially contagious between socially close individuals, which also suggest that yawn infectiousness may be an empathy-based.
National Health and Medical Research Council fellow, Dr Bernadette Fitzgibbon, of Monash University, has researched empathy for more than 10 years and agreed with the new study.
"It's an interesting study that looks at the real world with real people and looks outside of it [yawning] being a physiological response. People might have thought it was just a reflex," she said. "This study shows that it's a reflex that is enhanced by how close you are to a person."
Dr Fitzgibbon said there were clear differences between females and males and how they are made up.
"When you are made up of different hormones you can respond differently to situations, yawning may be one," she said. "[The study] makes sense when they say there are many differences between females and males because of hormones levels and that it may have an impact on yawning.
"It's important to remember that the overall finding is not a gender difference, it shows that contagious yawning is more dominant in social groups with females than males."
Yawning is an involuntary natural sequence of mouth opening with deep inspiration and slow expiration. An average human yawn last six seconds.
