The length of the yawn can predict how heavy a species' brain is. Yawn seems to correlate with the size of the brain, not the size of the body
Yawning is something you cannot control. A big, jaw-extending yawn can be embarrassing at certain moments because it gives the impression that you are bored, sleepy or not interested in a task or conversation.
Nevertheless, yawning is an important thing. Prior researches suggest that it increases the blood flow to the brain, which helps heat moves away and cools down the brain. But humans are not the only ones who yawn. The behavior is prevalent in animals too. Animals ranging in size from as small as mice to as big as elephant all have shown the ability to yawn.
Recently, researchers from State University of New York at Oneonta have attempted to evaluate the duration of the yawn of 29 mammal species, including mice, foxes, rabbits, walruses, elephants and humans. Researchers believe that the length of the yawn can predict how heavy a species' brain is and how many cortical neurons it have. That means mammals with bigger brains will logically need more brain tissues to cool down. Thus, they should have longer yawns. So in the study, researchers watched YouTube videos of different yawning animals and calculated the average length of their yawns.
When researches compared those numbers, they found that gorillas, horses, lions and elopements all have shorter yawns than humans despite their massive sizes. But it makes sense because the brains of these animals are smaller than ours. Precisely, humans had the longest average yawn, lasting 6.5 seconds. In contrast, tiny mice had a just 0.8 second yawn on average. African elephants, whose brains are close to the same weight as humans, almost had the same duration of yawn. The findings show that yawn is a reliable predictor to evaluate the size of a brain, irrespective to the size of creature’s body and also add supports to the hypothesis that yawning has positive effects on brain.
“These combined effects represent a striking scaling relationship between brain and behavior. Importantly, neither the size of the body nor the anatomical structures specific to yawning are driving these effects…yawning may have the dubious distinction of being the least understood, common, human behavior’. Unfortunately, 30 years later, we still know relatively little about the biological significance of this evolutionarily conserved response."
"Based on the current findings, we beleive yawn duration deservers further attention," Study concludes.