Yawning, an involuntary reflex commonly linked to fatigue, boredom, or stress, may play a more complex role in brain function than previously understood. A study published in Respiratory Physiology & Neurobiology, titled Biomechanics of contagious yawning: Insights into cranio-cervical fluid dynamics and Kinematic Consistency, suggests that yawning could influence the movement of fluid that protects the brain.

Researchers from the University of New South Wales conducted the study on 22 healthy participants. They were asked to yawn, breathe deeply, suppress yawns, and breathe normally while undergoing MRI scans to observe internal changes.

How yawning appears in MRI scans

Although yawning and deep breathing share similar physical traits, the scans revealed a key difference. During yawning, cerebrospinal fluid (CSF)—which cushions and protects the brain—sometimes moved away from the brain. In contrast, deep breathing showed the fluid moving in the opposite direction.

Researchers noted that this effect appeared less frequently in men, though they cautioned that this could be due to interference from the MRI scanner. However, both yawning and deep breathing were found to increase the outflow of blood from the brain, allowing fresh blood to circulate in.

Unique yawning patterns

The study also found that each individual exhibits a distinct yawning pattern. Neuroscientist Adam Martinac explained that while tongue movement differs between individuals, it remains consistent for each person—almost like a "fingerprint."

This consistency suggests the presence of a personalised central pattern generator in the brain that governs how each person yawns.

What could this mean?

While the exact purpose of these findings is still unclear, researchers are exploring possible explanations. Since CSF plays a role in delivering nutrients and removing waste from the central nervous system,yawning might help regulate or "clean" the brain. Another theory is that yawning contributes to cooling the brain, supporting its optimal functioning.

Overall, the study opens new avenues for understanding why yawning evolved in humans and other animals, pointing to a potentially important physiological role beyond simple tiredness or boredom.