If you have ever wondered why we yawn and also had your suspicions that it might be infectious or contagious the latest research on the topic will interest you.
In a study of autistic children, researchers at Birkbeck College, London say showing empathy has a lot to do with yawning.
The researchers tested the reaction of autistic children and normal children when watching video clips of people yawning and then simply moving their mouths.
They say what they discovered supports evidence that people who identify better with others are more prone to contagious yawning.
Atsushi Senju, a researcher at the university says scientists have always known that one yawn often leads others to follow suit but what triggers the phenomenon is unclear.
A yawn, when the mouth is opened wide is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or a lack of stimulation.
A yawn gives a powerful non-verbal message with several possible meanings, depending on the circumstances and some people believe a mechanism in the brain that makes people feel empathy also causes them to yawn when they see others doing the same.
Another speculated reason for yawning is nervousness which encourages the notion that yawning is a form of communication.
On average a yawn lasts about six seconds and 55 percent of people will yawn within five minutes of seeing someone else yawn; reading about yawning will make you yawn and Olympic athletes often yawn before competition.
For the study the researchers showed videos of people yawning or making other mouth movements to 24 children with autism spectrum disorder and to 25 normally developing children.
The researchers found the children with autism, a developmental condition that severely affects social interaction and communication including empathy, yawned less than other children during clips of people yawning.
The team found both groups of children yawned the same amount when watching the video of people only moving their mouths, showing that empathy was the key.
The researchers say their findings support the claim that contagious yawning is based on the ability for empathy.
Contagious yawning is seen in only a few other primates and studies have suggested the behaviour has played an evolutionary role in helping groups avoid danger by keeping animals awake and alert; cats, dogs, and even fish yawn.
The researchers suggest the findings are a trigger for research into the nature of social and communication impairment in those with autism.
They say more research is needed into the relationship between contagious yawning and other symptoms of (autism) such as empathy, imitation and/or face fixation.
The study is published in the Royal Society's Biology Letters.