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Yawning is usually associated with boredom or being tired, but new research suggests there's far more to this behavior than meets the eye.

The first clue that yawning serves a much greater purpose?

We do it involuntarily, like breathing, and it starts even before we're born (as early as 11 weeks after conception).

There are a number of theories out there for why we yawn, but one of the most compelling is being explored by a Princeton University researcher and his colleagues, whose studies suggest yawning performs the important function of cooling your brain.

Yawning Might Keep Your Brain Cool

A study in Animal Behaviori explains the hypothesis that "yawning serves as a thermoregulatory mechanism that occurs in response to increases in brain and/or body temperature.

The brain-cooling hypothesis further stipulates that, as ambient temperature increases and approaches (but does not exceed) body temperature, yawning should increase as a consequence."

Indeed, previous research by Andrew C. Gallup, PhD, now a postdoctoral research associate at Princeton University, and colleagues revealed that frequency of yawns more than doubledii among parakeets when their ambient temperature increased.

New research, this time on humansiii, also showed that more people yawned when it was winter compared to when it was summer (45 percent versus 24 percent, respectively), which supports Gallup's theory that people should yawn more in cold weather because the cool air you inhale helps regulate your brain temperature.

He told Discovery Newsiv:


"Brains are like computers... They operate most efficiently when cool, and physical adaptations have evolved to allow maximum cooling of the brain."

To put it simply, it's theorized that the influx of cool air that occurs when you yawn helps cool and increase blood flow in your neck, face, sinuses and head, which together acts like a radiator to cool your brain. Writing in the journal Medical Hypothesesv, Gallup and colleagues suggest this process may also involve your sinuses (the actual function of which is also up for debate):


"The thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling. Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds."

This finding is in line with previous research that shows brain temperatures increase when you're sleep deprived, which may be one reason why exhaustion triggers excessive yawning. Gallup also suggests that excessive yawning may even be a symptom of health conditions that increase brain and/or core temperature, such as central nervous system damage.

Dr Mercola
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