The Mystery Behind Yawning: What’s Really Going On?

Everyone has yawned before and everyone knows about yawning, but few understand the reason why we do it. I’ve heard so many different theories and ideas, but now that I am doing research, I wanted to investigate this question: why do we yawn? It turns out that no one knows for sure. However, based on my research of the literature, I've gathered and summarized some notable hypotheses.

Respiratory Hypothesis

One hypothesis about yawning is known as the respiratory hypothesis, which suggests that yawning is a way for your brain to get a lot of oxygen very quickly (Guggisberg, et al., 2010). Yawning may be triggered by high levels of carbon dioxide or low levels of oxygen in your blood (Provine, et al., 1987). A deep inhale and exhale that occurs when we yawn increases oxygen supply to our body. An experiment done in 1987 tested participants by having them inhale gases high in carbon dioxide, to determine if higher levels of carbon dioxide in blood lead to more yawning (Provine, et al., 1987). They also had participants exercise to lower their oxygen levels and see if yawning increased. They found that when participants were put in situations with high carbon dioxide or low oxygen levels, they didn’t yawn more often. Scientists have since noticed that our body has other ways to quickly get oxygen or decrease carbon dioxide (Guggisberg, et al., 2010). For instance, rapid breathing is common for people exercising and is more efficient for raising oxygen levels. These results and other studies suggest that the respiratory hypothesis is unlikely to be the primary function of yawning.

Arousal Hypothesis

Another notable theory is the arousal hypothesis, which suggests that yawning helps people to wake up when they feel tired or drowsy (Guggisberg, et al., 2010). Many people can relate to this and many experiments show that yawning can happen when you feel tired, which may mean that yawning has a connection to sleepiness (Catli, et al., 2015). Certain waves in your brain are associated with sleepiness or wakefulness, and can be measured by a device called an electroencephalography (EEG). Scientists used an EEG to monitor alpha waves in your brain, which can indicate becoming sleepier or becoming more alert (Guggisberg, et al., 2010). They compared the data from before yawning to after yawning. They found that there was no increase in alpha waves after the yawn, and instead a slight decrease, which indicates that the participants became more tired after the yawn. Similar results from several other studies using an EEG also seem to disprove the arousal hypothesis, suggesting that this also is not a main reason for yawning.

Social/Communication Hypothesis

In 2025, the leading hypothesis behind yawning is the social or communication hypothesis. Yawning can be dated back to ancient times and can also be seen in animals, which makes scientists think that there is an important social function behind it (Guggisberg, et al., 2010). The idea states that the primary function of yawning is to help communicate in groups, and sometimes to send a message that some think might say, “I am uncomfortable, but not in immediate danger.”

Another noted aspect of yawning is that it can be contagious (Poole, et al., 2023). Most people have probably noticed the urge to yawn after watching someone else yawn, an idea that scientists wanted to explore and answer. A study done in 2021 explored the idea of contagious yawning. They found that people are more likely to yawn after being shown a video of someone else yawning than the baseline video of nature (Poole, et al., 2023). They also identified a connection between contagious yawning and willingness to help others. They tested participants by pretending to have trouble using Zoom, and noted which people offered to help. The results were significant and showed that people who yawned after the videos were also more likely to offer help to the experimenter (Poole, et al., 2023). This relates to another social aspect that is often connected to yawning: empathy. Many people have at some point heard that yawning with other people is a sign of empathy. While theories that are based on difficult to measure ideas like empathy can be hard to prove, a few studies have started to find a connection. Based on all of the studies, the social hypothesis can explain some aspects of yawning.

Conclusion

There are still no definitive answers to the question of why we yawn, but scientists are continuing to research these ideas further. All of these theories, disproved or not, can still help us better understand ourselves and why we yawn. The current information has the best support for the social hypothesis and will continue to do more research and learn more about mysterious functions of our bodies. Until then, let’s keep yawning, as it may be our body saying, “Hang tight, the next exciting aspect of my life is loading… please stand by.”

Written by Kinsey Nichols and Edited by Aldrin V. Gomes, PhD

References

Guggisberg, A. G., Mathis, J., Schnider, A. & Hess, C. W. (2010). Why do we yawn? Science Direct. https://www.sciencedirect.com/science/article/pii/S0149763410000825?via%3Dihub#bib36. 

Provine, R. R., Tate, B. C. & Geldmacher, L. L. (1987). Yawning: No effect of 3-5% CO₂, 100% O₂, and exercise. Behavioral and Neural Biology. https://www.sciencedirect.com/science/article/pii/S0163104787909447 

Poole, K. L. & Henderson, H. A. (2023). Social Cognitive Correlates of Contagious Yawning and Smiling. Human Nature. https://link.springer.com/article/10.1007/s12110-023-09463-1#Sec9 

Catli, T., Acar, M., Hanci, D., Arikan, O. K. & Cingi, C. (2014). Importance of yawning in the evaluation of excessive daytime sleepiness: a prospective clinical study. European Archives of Oto-Rhino-Laryngology. https://link.springer.com/article/10.1007/s00405-014-3302-1