Q: Is there a physiological or neurological reason why people yawn? Why does yawning seem contagious?
A: Yawning is an involuntary action that causes us to open our mouths wide and deeply inhale. Yawning has been observed in animals and humans as young as 11-weeks old.
Yawning can be associated with fatigue, stress, or boredom. However it is not completely known why people yawn or what purpose is served. The following are several theories on the subject:
Boredom Theory - Yawning is thought to be caused by boredom, fatigue or drowsiness. A yawn leads to an increase in heart rate, blood pressure, and brain activity therefore, increasing human alertness or readiness.
Physiological Theory – The theory is that our bodies will involuntarily induce yawning to increase our oxygen uptake and remove excess carbon dioxide. However, clinical research has shown that yawning did not decrease in subject’s when additional oxygen was given to them or when carbon dioxide levels were reduced in the subject’s environment.
Evolution/Group Behavior Theory – Some researchers believe that prehistoric man would yawn and show their teeth as a way to intimidate others. Others believe that yawning was a nonverbal signal to communicate a change in group activity was needed, to communicate the general alertness of the group, or as a way to communicate the start and end of the day.
Brain-Cooling Theory – The theory suggests that yawning is a way of controlling brain temperature. A yawn is thought to cool your brain as ambient air temperatures increase in the subject’s environment. Some research has linked increased ambient temperatures with unpleasant symptoms associated with certain medical conditions.
Is Yawning contagious? - Yes, but it is not completely known why. One study found that consciously or subconsciously humans will react to another human yawning. As suggested in the evolution theory, yawning may be a form of prehistoric group behavior that is still evident today.