Did you grow up being told that people yawn in a meeting or classroom because they're bored? Whenever I yawned in childhood, I was often told to stand up straight because “you’re doing shallow breathing and are oxygen deprived.” Those may be triggers but researchers now suggest that sleep-deprivation may also trigger yawning. The involuntary behavior of yawning (it’s difficult to produce a genuine yawn on demand) may be designed to cool down brain tissue. The temperature of your brain increases when you are sleep deprived. Yawning causes you to take in deeper breaths of air. Inhaling cool air ventilates your sinuses and helps to dissipate heat. This is another way in which human brains resemble computers: computers and human brains work best when cool. More tomorrow.