The Physiology of an Uninhibited Yawn
A full, unrestricted yawn is a coordinated, complex physiological event involving multiple body parts, primarily controlled by neurotransmitters in the hypothalamus. A typical yawn lasts between four and seven seconds and follows a distinct pattern:
- A slow, deep inhalation causes the diaphragm and rib muscles to contract.
- The jaw opens wide, stretching muscles in the face and throat.
- Your soft palate and parts of your pharynx rise, and the eustachian tubes in your ears may pop.
- A brief climax of muscle tension is reached.
- A slow exhalation and a relaxing of the jaw and other facial muscles concludes the process.
The most prominent theories for the function of a yawn today are not about increasing oxygen levels, a theory that has been largely discarded. Instead, evidence points to other roles:
- Brain Cooling Hypothesis: The deep inhalation of air and increased blood flow cools the brain when its temperature rises.
- Arousal Hypothesis: Yawning can occur during transitions from a low-activity state to a higher one, such as waking up or before a stressful event, helping to increase alertness.
- Ear Pressure Equalization: The muscle movements help to open the eustachian tubes, equalizing air pressure in the middle ear.
- Airway Patency: Yawning may help reposition and stretch the muscles around the airway, particularly in the pharynx, which can collapse during low-vigilance states.
The Incomplete Sensation of a Stifled Yawn
When you attempt to stifle a yawn by keeping your mouth closed, you are actively inhibiting a complex, involuntary motor program. This suppression prevents the gaping of the jaw, which is an essential part of the full sequence. What you experience is a muted version of the reflex, characterized by:
- An uncomfortable, 'stuck-in-mid-yawn' sensation.
- The sensation of air being forced out through your nose, though it may not provide the same relief as a full oral exhalation.
- A residual urge to yawn that remains because the initial physiological command was not fully completed.
The result is a less rewarding experience that fails to deliver the sense of relief and heightened alertness that a full yawn can provide. This is because the physiological mechanisms intended to be activated, like the full stretching of facial and pharyngeal muscles, are inhibited.
Are There Any Dangers to Suppressing a Yawn?
For most people, deliberately stifling a yawn is not dangerous and will not cause serious harm. The primary consequence is simply the feeling of frustration or the need to yawn again shortly after. However, some research has explored minor potential issues related to consistent suppression or social inhibition of yawns.
Psychological and Physical Discomfort
- Anhedonia: The feeling of frustration from an incomplete yawn is sometimes referred to as anhedonia within yawning studies. It is the result of the body’s reflex not being harmoniously developed. The feeling is temporary and not a cause for concern.
- Tonsil Considerations: A study from 2012 raised a speculative hypothesis about the potential for endemic tonsillitis in Western societies due to social pressures to suppress yawns. The theory suggests a full yawn might help evacuate the tonsillar fossae, but the evidence is not widely supported.
While these considerations are minor, they underscore that the body's natural reflexes, even ones as seemingly simple as a yawn, serve a purpose, and overriding them can come with slight, though temporary, downsides.
Full Yawn vs. Stifled Yawn Comparison
| Feature | Full, Open-Mouthed Yawn | Stifled, Closed-Mouthed Yawn |
|---|---|---|
| Sensation | Rewarding, satisfying, and complete. | Incomplete, awkward, and frustrating. |
| Physiological Action | Deep inhalation, full facial and pharyngeal muscle stretching, jaw gaping. | Inhalation is limited, facial muscles are clenched, jaw gaping is inhibited. |
| Potential Benefit | Maximum effect on brain cooling, arousal, and ear pressure equalization. | Minimal effect; primary functions of yawning are not fully realized. |
| Exhalation Path | Primarily through the mouth. | Primarily through the nose, feeling trapped. |
How to Manage a Yawn in Public
Instead of clenching your jaw to suppress a yawn, which can leave you feeling restless, try these less disruptive methods to manage the urge:
- Deep Nasal Breathing: Take a few deep, slow breaths through your nose. This can sometimes interrupt the reflex.
- Cool Down: Since a primary theory for yawning involves cooling the brain, try drinking a cool beverage like ice water or stepping into a cooler area.
- Change Your Activity: If you are bored, getting up and moving around can help increase your heart rate and alertness, reducing the need to yawn.
- Discreetly Conceal: If you must yawn, it's considered more polite to cover your mouth with your hand or sleeve rather than attempting to painfully stifle it.
Conclusion
Ultimately, consciously deciding what happens if you don't open your mouth when you yawn reveals that you can interfere with the body's natural reflex, but not without consequences. While suppressing a yawn is not dangerous, it prevents the rewarding culmination of the physiological process and leaves the body's need unaddressed. The stifled yawn is a clear example of how complex and interconnected our involuntary bodily functions are, and in most cases, it is best to simply allow the reflex to run its course. For those times when discretion is needed, managing the urge through alternative, less disruptive methods is a more effective and comfortable approach than fighting the powerful urge itself.
For more on the potential consequences of inhibiting this reflex, read the article "Born to Yawn? Understanding Yawning as a Warning of the ..." from the National Institutes of Health.(https://pmc.ncbi.nlm.nih.gov/articles/PMC3626133/)
