WebMD Human Anatomy

Human anatomy term paper

All humans yawn. So do most vertebrate animals. Surely it serves some useful function. But what that might be has puzzled scientists throughout the ages.

"We have collected data on rats, parakeets, and humans. All the data supports the brain-cooling hypothesis, " Gallup tells WebMD.

Here's the basic idea:

  • The deep intake of breath during a yawn forces downward flow of spinal fluid and blood from the brain.
  • Cool air breathed into the mouth cools these fluids.

To answer skeptics, Gallup has laid out a more detailed anatomical description of the process in the medical literature.

We Yawn More When It's Cool

Gallup's theory predicts that colder outside air should cool the brain better than hot air. The body should therefore yawn more when the air is cool, and yawn less when the air is hot.

Where better to test this than in Tucson, Ariz.? Gallup's team went there twice: Once in the winter, when it was a cool 71.6 degrees F outside, and once in early summer, when it was 98.6 degrees F.

The researchers asked 80 pedestrians to look at pictures of people yawning. It's well known that people often yawn when they see others yawn.

Sure enough, in the cooler weather 45% of people yawned when they looked at the pictures. But in hotter weather, only 24% of people yawned. Moreover, people yawned more if they'd been outside longer in the cool weather, and yawned less if they'd been outside longer in the hot weather.

These results mimicked an earlier study in which Gallup's team showed that budgie parakeets yawned more in cool temperatures than they did in hot temperatures. And it supported a rat study in which rat brains cooled a bit when the animals yawned.

What We Say When We Yawn

Gallup says his brain cooling theory of yawning is the only theory that explains all these experimental results. But he has not yet convinced those who prefer another theory.

University of Geneva physician Adrian G. Guggisberg, MD, agrees with Gallup that changes in room temperature can trigger yawning. But he's wary of the brain cooling theory. And he offers an alternative interpretation of Gallup's Tucson study.

"The fact that yawning is suppressed during high temperatures suggest that it fails precisely when we need it, " Guggisberg tells WebMD. "There are other [ways to regulate body temperature], such as sweating, and it is unclear why we would need another regulator which fails when it matters."

Yawn theorists split into two camps. Like Gallup, one side says yawning must have a physiological cause, and a physical benefit. The other side says yawning is a form of communication that offers various social benefits.

Guggisberg prefers the social theory of yawning. He sees the physiological effects of yawning as too small to account for their persistence through evolution. But he sees the contagious effect of yawning as a key clue.

"The more people are susceptible to contagious yawning, the better their social competence and empathy, " Guggisberg says. "In humans it is clear that yawning has a social effect. It is probably an unconscious behavior. It is not clear what yawning communicates or what it achieves. But clearly it transmits some information that has some effect on brain networks or behavior."

Across cultures, Guggisberg says, the yawn is understood as a sign of sleepiness and boredom. The yawn thus communicates to others that one is experiencing a moderately unpleasant experience but not an immediate threat.

"We might have to get used to the idea that yawns have a primarily social rather than primarily physiological effect, " Guggisberg and colleagues wrote in a recent article.

Gallup argues that whatever message yawning communicates, it is far too ambiguous and subtle to be so well-conserved throughout evolutionary history.

"It is not that I don't think there is any social function to yawning, because clearly it is contagious, " Gallup says. "But we have to think of it as a process driven by physiological triggers we are unable to control. If it happens in a meeting, it should not be a sign of disrespect or insult."


The Gallup study appears in the Aug. 28 online issue of Frontiers in Evolutionary Neuroscience.



Andrew G. Gallup, PhD, postdoctoral research associate, department of ecology and evolutionary biology, Princeton University, New Jersey.

Adrian G. Guggisberg, MD, division of neurorehabilitation, University of Geneva, Switzerland.

Gallup, A.C. and Eldakar, O.T. Frontiers in Evolutionary Neuroscience, published online Aug. 28, 2011.

Shoup-Knox, M. Frontiers in Evolutionary Neuroscience, published online Sept. 24, 2010.

Gallup, A.C. and Gallup, G.G. Evolutionary Psychology, 2007; vol 5: pp 92-101.

You might also like

False Memory - Surveillance / Überwachung
False Memory - Surveillance / Überwachung
FALSE MEMORY BY DAN KROKOS | book review + book discush
FALSE MEMORY BY DAN KROKOS | book review + book discush
創‧憶 False‧Memory》微電影預告片
創‧憶 False‧Memory》微電影預告片
False Memory.
False Memory.
Classic Brands Classic Brands Conforma Memory Foam Pillow, Queen
Furniture (Classic Brands)
  • Pressure Relieving Memory Foam, Memory Foam Is Hypo Allergenic And Dust Mite Resistant
  • Ventilated Memory Foam With Cool Sleep Technology
  • Soft Velour Cover
  • over is Removable and Washable
  • Designed For All Types of Sleepers, Cradles Head & Neck In Proper Sleep Position
  • 5 Star Customer Service
Kittrich Memory Foam Kidz Standard-Size Memory Foam Pillow, Beige
Home (Kittrich)
  • 100-percent visco elastic memory foam.
  • Waterproof, hypoallergenic and mite-proof.
  • Permanent plush velour cover.
  • Standard size: 19 x 25 x 4
Omron Omron 5 Series Upper Arm Blood Pressure Monitor with Cuff that fits Standard and Large Arms (BP742N)
Health and Beauty (Omron)
  • No. 1 doctor and pharmacist recommended brand and #1 selling Manufacturer of Blood Pressure Monitors for 40 years
  • Feel empowered by accuracy with technology that automatically displays the average of your last 3 readings taken within 10 minutes
  • Quickly see how your reading compares to normal home blood pressure levels with the BP Level Indicator
  • Alerts you instantly if an irregular heartbeat is detected while your blood pressure is being measured
  • Increased memory storage allows you to monitor and store the last 100 readings for more than one person
Crucial Crucial 8GB Single DDR3L 1600 MT/s (PC3L-12800) SODIMM 204-Pin Memory - CT102464BF160B
Personal Computer (Crucial)
  • Increases system performance
  • Easy to install
  • Premium quality memory from a trusted brand
  • DDR3 & DDR3L are the same thing (DDR3L stands for DDR3 Low voltage and applies to our 1.35V DRAM)
  • This is a dual voltage piece and can operate at 1.35V or 1.5V
Automatic Wrist Blood Pressure Monitor by HealthyWealthy, Digital Sphygmomanometer BP Cuff, High Accuracy Measurements for high blood pressure , Apparatus for Measuring Pressure
Health and Beauty (HUAAN)
  • HOME HEALTH MANAGEMENT: Keeping track of your blood pressure is important for your health management, especially when there are hypertension problems. One cannot...
  • EASY TO USE: It is no trouble and uncomplicated to use the HealthyWealthy blood pressure monitor. Simply apply the cuff on your bare wrist and wrap it around for...
  • EXACT MEASUREMENTS: Our device has been tested and compared with the best scientific sphygmomanometers. Its measurements have been found within the accuracy limits...
  • STORE AND COMPARE RESULTS: For complete blood pressure management, our monitor allows you to store up to 60 measurements so you can compare and keep track of your...
  • LIGHTWEIGHT AND ADJUSTABLE CUFF: Small and easily packed, you can carry our blood pressure monitor in any bag or purse at any place, its cuff can fit wrists of size...

Copyright © . All Rights Reserved