Yawn is an involuntary reflex to having less oxygen in our body than we require. If you are bored or tired your breathing will slow down which will cause you to take in less oxygen and so your body will trigger a yawn to help breathe in more. 

It has also been suggested that yawn is a way of cooling your brain, to avoid the brain overheating. In short, more people yawn in summer than in winter. It is a way of increasing your heart rate, blood flow and the use of muscles in the face which all help cool down the brain.

Your brain is more likely to overheat when you are exhausted or sleep deprived so this is why you yawn at these times. But if this is the cause of yawning, why is it that when you see someone yawning, why do you yawn in response?

Contagious yawning is not as scary as it sounds and we have all experienced it before. When someone else yawns, we yawn. When someone talks about yawning, we yawn. The sound of a yawn makes us yawn.

There are many theories as to why this occurs, some say it is to do with empathy, others say it is us imitating others because of neurological stimulation.

Contagious yawning begins when a child is about four or five years old, this is also the age when a child begins to develop empathetic behavior and when they begin to recognise emotions in others.

You are more likely to yawn in response to someone socially or genetically close to you, dogs are more likely to yawn in response to their owner’s yawn. The other theory is that contagious yawning is caused by mirror neurons. These neurons fire both when an animal acts and when an animal sees another animal act.