REFLEX
1 WHY WE YAWN
t was previously accepted that we yawn to draw in oxygen because we breathe slower when tired or bored. However, an experiment carried out at the University of Baltimore in the US changed oxygen levels and found no change in yawning. Some scientists now think we do it to cool our brains. A team at the State University of New York at Albany discovered that chilling people’s foreheads stopped them yawning, and that we do
