Scientists have now studied something as mundane as animals' yawn. Surprisingly, they found out that the duration of an animals' yawn is linked to the physiognomy of the animal's brain.
It seems like animals' yawn is not related to how bored they have been at that moment in time. Researchers who studied the different yawns of 29 mammals, including a turtle, polar bear, snake, iguana and humans, discovered that the longer or shorter the yawn depends on underlying neurological differences.
The research indicates that the motor action pattern in yawning promotes a certain function. It confirms the long-held hypothesis that yawning enhances the arousal of brain cortex and changes the state of the brain through enhanced intracranial circulation and brain cooling.
The openly accessible data used by the researchers interrelate the contrasting yawn duration to mammalian brain weight and cortical neuron number (ρ
-values > 0.9). The number of neurons in the mammal's brain cortex is a robust predictor of the standard variability of the animal's yawn duration.
An article in Science
explains the pattern and draws conclusion from it. It states that small-brained animals with fewer neurons in the wrinkly outer layer of the brain, called the cortex, had shorter yawns than large-brained animals with more cortical neurons.
The report showed that primates tend to yawn at a rate of 6 seconds average which is a rate longer than other non-primates and humans. Tiny brained animals like mice for instance holds yawn that is in a shorter rate of 1.5 seconds.
So next time you watch an animal yawn, think about how much weight and how big its brain is.