Yawning is often associated with tiredness, boredom, fatigue or hunger, but why do we actually do it?
Well, the short answer is, no one really knows. It's been the topic of discussion and research for years, but the cause of this seemingly odd and inconsequential bahaviour has never been properly confirmed.
Scientific studies have managed to conclude however, that yawning could provide a social or a physiological function or a little bit of both.
"It's a little bit tricky because we can never say that something is completely biological, there is always a learning or a cultural component to it,'" Associate Professor Darren Curnoe told HuffPost Australia.
Socially, research suggests that yawning has to do with bonding, where we are more likely to yawn if someone that we share a relationship with, like a partner, parent, sibling or close friend does so first. This is why yawns are contagious.
"We tend to yawn much more often, and without thought, when people we are close to yawn. We don't tend to yawn as often when we are with people that we don't know.
"So, that suggests that there is some kind of social function to yawning, and that it has something to do with some kind of closeness with relationships," Curnoe said.
Yawns could also be related to social conditioning and learned behaviours.
"When we are infants, we're observing the world and observing other adults and our peers and we do an awful lot through vision. So, we see the way they [people around us] behave and the way they respond and we imitate," Curnoe told HuffPost Australia.
"It's always quite tricky, we never know whether other kinds of behaviours are learned when we are very young ... and if there is a learning component to these behaviours."
On the communicative side, yawning behaviors also exist in other primate species and usually serve the function of displaying dominance or intention to intimidate by exposing the large canine teeth.
"If we think about how it might apply to humans, of course we don't have large canine teeth, so the question would be, is it kind of an evolutionary hangover, if you like, from our early primate origins?
"I don't think we understand what the signal is and what a yawn actually means, apart from [the] cultural explanations for things, but from an evolutionary view point, we really don't understand what function a yawn serves and what the message is that its conveying."
Physiologically, yawning could help in providing our bodies with oxygen when we need it, but this is hard to prove.
"Yawning may have some kind of physiological basis, for example, one of the ideas is that we yawn because it gives us a quick intake of oxygen and that may be a physiological response to low blood oxygen levels. So, that is one of the theories, but it has been incredibly difficult to prove that this is the case," Curnoe said.
So essentially, why we yawn is still a bit of a mystery, especially because there seems to be so much involved socially, culturally and biogically.
"That's the complexity when you are dealing with these kinds of human behaviours, that you have to try and tease out these social or these cultural contexts as well [as the biological ones]."