Big yawns are a sign of having a large brain

Friday, October 14, 2016 by: Daniel Barker
Tags: yawning, brain size, study

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(NaturalNews) Yawning in public may be considered slightly rude - but it's also a sign having a large brain, according to new research.

Psychologist Andrew Gallup of State University of New York at Oneonta, recently conducted an experiment in which student participants were instructed to find videos of animals yawning - animals chosen from a list that included gorillas, cats, elephants and other species.

The list of 24 mammals was taken from an earlier research paper on brain evolution that measured the brain weight and cortical neuron density of various animals. The cortex is the part of the brain responsible for higher brain functions.

The bigger the brain, the longer the yawn

When Gallup and his colleagues reviewed the videos, they found a surprisingly strong link between the two brain traits and the length of yawns displayed by the various animals selected for the study.

The team saw that the longer the yawn, the more brain weight and number of neurons in the cortex of the animal.

From The Atlantic:

"Put it this way: If you take a mammal and time its yawn, you can reasonably predict how heavy its brain is and how many cortical neurons they have. 'We were just really blown out of the water,' says Gallup. 'It's such a strong predictor.'"

What purpose does yawning serve?

There are competing theories regarding the function of yawning. Gallup dispels the common myth that yawning helps to increase oxygen levels in the brain, but believes that yawning behavior evolved for a particular physiological reason. What that reason might be is a subject of hot debate, according to Gallup.

One theory proposes that yawning is social behavior that involuntarily signals empathy. Proponents of this theory point to the fact that contagious yawning is observed only in very social species, but this explanation has been disputed and regardless doesn't account for yawning observed in solitary animals.

Gallup's favorite theory is that yawning actually serves as a brain-cooling mechanism:

"When you yawn, you constrict and relax your facial muscles, increasing the flow of warm blood around the skull, and allowing some of that heat to radiate into the surrounding air. Yawning also involves a deep inhalation, which brings cool air into nose and mouth, chilling our blood from within."

This explanation is backed by solid scientific evidence - Gallup monitored the brain temperature of rats and found that yawning did indeed cool the brain down when overheated.

The reason we yawn when tired also is apparently tied to body heat. In the evening our body temperatures are at their highest, therefore we tend to yawn at the end of our day when we are also tired, says Gallup.

Gallup reasoned that if yawning serves to cool the brain, it might be predicted that animals with larger brains would require longer yawns. That's exactly what the team found when observing the animals in the videos - but the samples were too few to draw too many definite conclusions, warned Liz Cirulli Rogers of Duke University School of Medicine. "This could be an important and interesting observation, though," she said.

Gallup accepts the criticism and hopes that his team's preliminary research will lead to bigger studies in the future.

You may be yawning now while wondering why this study is so important, but there may be important lessons to be learned from exploring the origins and function of yawning behavior in animals and humans:

"If you look within a single species, does the length of a yawn relate to an individual's brain traits or mental skills? Could it be an early sign of brain damage?"

The answers to these questions could reveal something worthwhile - after all, yawning is one of the least understood human behaviors.

Sources:

PBS.org

TheAtlantic.com