Why do we yawn?
Show answer & explanation
Answer: Still unclear, possibly cooling
Excess carbon dioxide buildup — Wrong. CO₂ levels don't trigger yawning. Research shows no strong connection between yawning and respiratory gas exchange.
Brain temperature needs cooling — Wrong. Brain cooling is one leading hypothesis—yawning increases blood flow and may help thermoregulate, but it's not definitively proven.
Still unclear, possibly cooling ✓ — Correct! Yawning's function is surprisingly unclear! Leading theories: (1) Brain cooling—jaw stretching increases blood flow, cooling the brain. (2) Arousal/state change—transitions between sleep/wake states. (3) Social communication—contagious yawning suggests social bonding function. Not caused by low O₂ despite popular belief. Likely multifunctional evolutionary behavior!