Group behaviour:Yawning is contagious and a research group from the University of Leeds believes they know the reason why - evolution. It is down to showing you are in tune with your peers and may also have helped prevent your group from being eaten by predators.
"Yawning isn't unique to humans, lots of animals yawn: snakes yawn and hippos yawn," stated Leeds psychology lecturer, Dr Catriona Morrison.
It is much more than a signal for being tired or bored. "Yawning has the effect of increasing cerebral blood flow, it perks us up."
Dr Morrison's research, presented yesterday at the annual BA Festival of Science in York, also found that the tendency to yawn in unison with those around you is also a measure of empathy. Those more likely to yawn with others are also 60 per cent more likely to score high on tests measuring your level of empathy for others.
Dr Morrison describes empathy as "the extent to which you have an appreciation of other people's mental states", something that animals cannot achieve. "Yawning contagiously is something uniquely human," she said. "What we want to learn is what it tell us about the mind."
She set up a small study involving 80 people, a mix of engineering and psychology students, to measure the level of contagious yawning. They were asked to participate in research and were told to wait in a room, but as Dr Morrison stated, "in fact they were already in an experiment".
A planted individual in the room began yawning, completing 10 yawns in 10 minutes. Just under two-thirds of subjects yawned in response. The yawners and non-yawners were then given a battery of tests to gauge their level of empathy. Virtually all of the yawners scored high on this test, Dr Morrison said.
Unexpectedly, men and women scored equally well. "We were interested in the sex differences as females are meant to be more empathetic than males," she said. She found, however, that the engineers scored less well than the psychology students.
Understanding contagious yawning is even more complex, as children are not born with this ability, but acquire it probably when they can begin to experience empathy, Dr Morrison stated. Yet it is an unconscious and spontaneous signal, so it is not actually learned behaviour.
She believes there was an evolutionary selection advantage for sympathetic yawners. Mirror behaviour is common in humans and represents an acquired "social signal of empathy". You will be more empathetic and supportive of members in your group if they display the same behaviour for you.
But contagious yawning also would have helped survival when human-eating predators roamed the savannah as our species was emerging. "From an evolutionary point of view, it increases your ability to keep alert," Dr Morrison suggested.