The Physiological Theory is undoubtedly the most well-known theory explaining why we yawn, however it is the most loosely connected to scientific evidence. This theory emphasizes that we yawn in order to take in more oxygen, or expel a greater amount of carbon dioxide from our lungs. Yet, we do not yawn during exercise, or in situations of low oxygen/high carbon dioxide, depreciating the accuracy of this theory.

It was further thought that we yawn during times of boredom, such that yawning allows us to be more alert. This is called the Boredom Theory.

The most recent proposition that has emerged as of the late 2000’s is the Brain-Cooling Theory (or Hypothermia Hypothesis) by scientists Gary Hack and Andrew Gallup, of Princeton University. Human subjects were tested for yawning when their brains were either warm or cool. The temperature of the brain was elevated or depressed by placing hot and cold packs against their heads, respectively. It was discovered that subjects yawned more frequently when their brains were warmer rather than cooler, suggesting that yawning is a mechanism of cooling the brain. Similarly test mice were seen to yawn more frequently when the air was cooler, thereby increasing the ability of a yawn to cool the brain. Hack and Gallup put forward that the action of yawning lowers the temperature of the brain by expanding the walls of our maxillary sinus (the largest of our sinus cavities in the head), pumping air into the brain. Why, though, is a cool brain optimal? Cool brains work more efficiently (like a computer), and thus ameliorate our ability to carry out cognitive functions. Hence, having a cool brain allows us to be more alert and think more clearly.

An older, also feasible yawning theory is the Evolution Theory, which establishes that yawning may have had some evolutionary basis in our ancestors. Perhaps yawning was a way of communication, or intimidation.


The contagion of yawning is a very curious phenomenon, and for this reason, it is a valuable area of scientific study. Scientists have proposed that contagious yawning is a presentation of mimicry in human social interaction. This is also seen when we smile and others subconsciously smile in return, suggesting that yawning, like smiling, possibly has a strong connection to empathetic behaviour. This breakthrough has enabled scientists to study empathy in humans through the physical act of yawning. The relationship between yawning and empathy is more strongly pronounced in individuals with greater genetic or emotional connections (such that yawning is more contagious amongst family members and close friends). Children who have an Autism disorder are affected in their types of social interactions, and mainly do not possess the skill of empathy. Studies have shown that children without Autism yawn contagiously, meaning more frequently than children with Autism. These representations have opened pathways for doctors to be able to diagnose disorders in young children based on their capacity to yawn contagiously.


Insomniacs are inflicted by a difficulty in regulating their body temperatures, which must drop before sleep can occur. The realization that yawning is a mechanism to lower brain temperature has allowed scientists to envision new treatments for insomnia, which may involve manual cooling of the sinuses through medication or other means.

It is truly intriguing an abstract concept such as yawning has opened a plethora of avenues in understanding neuropsychological processes such as empathy in relation to Autism, as well as physiological mechanisms in sleep disorders. Surely, there is much more to learn about the science of yawning, especially since it has only recently emerged in methodical application.


By Hana Abbas

Please note that opinions expressed are the author’s own. They do not necessarily reflect the views and values of The Blank Page.