Researchers have linked brain size to yawning duration in mammals and birds.
- Yawning increases the flow of fresh blood to the brain and therefore has a thermoregulatory function.
- In mammals and birds, the duration of yawns increases with the size and number of neurons in their brains.
- “If the temperature of the brain, for whatever reason, rises too much, we are less alert and less attentive.”
We yawn between 5 and 10 times a day. It happens when you feel sleepy or hungry. Human beings are not the only ones to open their mouths by an involuntary contraction of the muscles of the face. This great inspiration has also been observed in vertebrates. For several years, biologists have wondered about the reasons for the evolution of yawning.
The bigger the brain, the more it needs to be cooled
“Recent research indicates that yawning has become a cooling mechanism for the brain. Since large brains have greater thermolytic needs and brain temperature is determined in part by heat production from neural activity , it was hypothesized that animals with larger brains and more neurons would yawn longer to produce comparable cooling effects,” said scientists from the University of Utrecht (Netherlands).
More than 1,250 yawns were collected
To verify their theory, they carried out a study published in the journal Communications Biology. As part of this work, the team collected 1,291 yawns from 55 mammals and 46 bird species. “We went to several zoos with a camera and waited for the animals to yawn. It was a lot of work. Getting video footage of so many animals yawning takes some patience. , and coding all those yawns made me immune to the contagiousness of yawning.”said Jorg Massen, author of the research, in a statement. Then, the authors linked the duration of these yawns to brain and neuronal data.
Vertebrates with larger brains yawn longer
According to the results, the duration of yawns in species increases with the size and number of neurons in their brains. The researchers found that the mammals seemed to yawn longer than the birds. According to them, this can be explained by the higher central temperature in the body of the birds. The difference between the central temperature of birds and the surrounding air is greater than in mammals. Therefore, a bird’s brain cools faster compared to ambient air, so a shorter yawn is sufficient.
“If the temperature of the brain increases too much, we are less attentive”
As a reminder, the brain works best at an optimal temperature. “If the temperature of the brain, for whatever reason, increases too much, we are less alert and less attentive. It seems today that mammals and birds have evolved a behavioral mechanism to counter this phenomenon. (…) We maybe we should stop seeing yawns as rude and appreciate that the person is trying to pay attention instead,” concluded Jorg Massen.
