Scientists performed a study to see if yawns help to cool down the brain and believe that it is the body’s natural reflex to do so. The study was published in the Physiology & Behavior journal and involved 92 undergraduate biology students.
These students changed the temperature of their brains in a lab to test the hypothesis that yawning is a result of the skull getting to hot. They believed that it cooled the brain by taking warm blood away while simultaneously bringing in a cooler supply.
A variety of factors can change the temperature of the brain, from stress to cortical arousal to sleep patterns and more.
Participants put a cold (4 C/39.2 F), warm (46 C) or room temperature (22 C) pack on their carotid arteries which are major blood vessels in the neck that pump blood towards the brain, neck, and face.
After five minutes of holding the compress in this place, the scientists checked to see if the brain temperature was altered; thermographic imaging equipment was necessary to accurately test this.
After, the participants watched a video of nine different people yawning for 63 seconds. At the end, they were asked to fill out questionnaires to see if they had any urges to yawn before, during, or after the video. The researchers thought this would be an effective test of yawns affecting brain temperature since yawns are contagious.
Their hypothesis was proved correct as brain cooling was associated with fewer urges to yawn. Just 62 of the participants felt the need to yawn during the video, and the participant who had cooled their brain temperature had less of an urge than those in warm and room temperature groups.
A total of 84,8 percent of those in the warm group felt like yawning while 69.2 of the room temperature group and 48.5 percent of those in the cool group felt the urge.
“These findings are consistent with previous research indicating that yawns function as a compensatory brain cooling mechanism,” the authors wrote.
However, the results of both the warm and room temperature groups were quite similar, so the researchers surmise that the heating back may have created too high of a temperature.
Andrew C. Gallup, study co-author and assistant professor of psychology at SUNY Polytechnic Institute, told PsyPost: “Yawning is often misunderstood both within the scientific community and the general public.”
In previous studies, Gallup and his team found that people are less likely to catch yawns during the winter than in the summer months. This study was also published in Physiology & Behavior in 2014.
Researcher Olivier Walusinski in the journal Clinical Anatomy in 2013 also theorized that the reason we yawn is to send cerebrospinal fluid around the brain.