There seem to be two types of yawns. The first is spontaneous yawning to increase the state of arousal. Boredom, fatigue and hunger all result in increased yawning. The second is contagious yawning, where we yawn in response to seeing, hearing or reading about yawning.
What is a yawn?
Yawning consists of the involuntary opening of the mouth, an inhalation of air combined with a stretching of the jaw and then a subsequent exhalation and a feeling of satisfaction. The average yawn lasts about 5 seconds. Stretching of the limbs often accompanies a yawn in humans. Stifling a yawn is not as satisfying as the full jaw stretching option.
When do we yawn? Yawns may be considered a universal sign of boredom and fatigue. In fact, recent studies have shown that yawning indicates a changing state of alertness in the body and a need for arousal. When we are bored, we pay less attention and our arousal levels decrease, hence we are prone to yawning. Yawning may be interpreted as disrespectful and can be quite embarrassing in certain situations. Imagine yawning in the middle of an interview! We also yawn when we are getting hungry – a characteristic we share with other primates.
Imagine waking up. We often stretch and yawn to wake up our bodies. At one time, it was thought that we yawn to increase the amount of oxygen intake in the lungs. Further research has shown that this is not the case. Even foetuses yawn in utero, where there is no air intake into the lungs. There is no difference in spontaneous yawning between neurotypicals and people with autism or schizophrenia. There is more spontaneous yawning in people with MS or brain damage.
Yawns as a contagious response:
Take a look at this photo.
Do you feel like yawning? Or maybe you did yawn. If you did, it’s not uncommon. In fact, yawns can be contagious by watching another yawn, hearing another yawn and even while reading about yawning. The contagion of yawns varies across people. For example, a recent study by Bartholamew and Ciruli (2014) found that some people can watch a 3 minute video of yawning and not yawn. Not only that, within this group, there were some that did not even feel like yawning. These researchers showed that empathy, time of day, or intelligence do not explain the variability. Age accounted for only 8% of the variability, higher age showing less contagion. Males are more likely than females to trigger contagious yawns, but females are more susceptible to contagious yawning compared to males. The authors suggest that there may be a heritability factor at play. Developmental level may also impact contagious yawning. Namely, infants do not yawn when they see their mothers yawn but preschoolers and older children do.
Empathy and Yawning
Scientists have proposed a link between yawning and empathy. Studies have shown, for example, that contagious yawning increases with the level of relationship. We will yawn more for an acquaintance versus a stranger, a friend versus an acquaintance, and this increases further with family. The tendency towards increased yawning with social bond, demonstrates a relationship between empathy and yawning. Further, in diagnoses with lower levels of empathy, such as autism and schizophrenia, there is decreased contagious yawning. However, greater contagious yawning is not necessarily related to higher levels of empathy. As written above, gender, age and heritability factors may all impact contagious yawning.
Yawning remains quite a mystery in science. If you read this whole blog post and didn’t yawn I am very impressed. While writing this I have yawned countless times, even though I find the topic quite interesting!