Healthcare professionals and researchers have observed human fetuses yawning as early as 11 weeks after conception. Many researchers regard the desire to yawn as a primal human instinct. Experts are not entirely sure why humans yawn, but one common explanation is that yawning stretches and lubricates the lungs. Yawning also increases a person's heart rate.
More about yawning:
- One study showed that people yawn more often during the colder winter months than they do during the summer. The researchers speculated that yawning might be a way for people to cool their brains — something that yawning in high temperatures would not accomplish, because the air that is breathed in would be warmer.
- Yawning can be contagious, but some research shows that it is less so in children who are less than 6 years old.
- In 2005, a US judge fined a juror for contempt of court after the juror yawned loudly in the courtroom.