Why is yawning contagious? 

Key points: 

• Yawning as a Widespread and Contagious Phenomenon: Yawning is a common and intriguing behavior experienced around 20 times a day by individuals. It becomes contagious in social settings, prompting the question of why it spreads among people.

• Scientific Theories on Yawning: Scientific experts, including a speech scientist and a neuroethicist, present various theories on yawning's evolutionary purpose and triggers. These theories involve respiratory functions, chemical changes in the body, and potential benefits such as cooling the brain or stretching internal organs.

• Social Mirroring and the Contagious Nature of Yawning: Yawning's contagiousness is attributed to social mirroring, where organisms instinctively imitate the actions of others. Studies indicate a sixfold increase in yawning likelihood after witnessing someone else yawn. This mirroring behavior, linked to mirror neurons, might serve a purpose in saving energy, protecting against diseases, and strengthening social bonds, with more empathetic individuals being more prone to such social mirroring.

Yawning is a fascinating and widespread phenomenon that each of us experiences, on average, about 20 times a day. It's a natural response that, once triggered, is challenging to resist. Yet, the intriguing question arises: why does the act of yawning seem to be contagious when we are in the company of others who are also yawning?

PBS News Hour delved into this captivating topic by consulting a panel of experts, including a speech scientist, a sleep neurologist, a neuroethicist, and a neuroscientist specializing in brain circuits related to itching. Although the evolutionary purpose of collective yawning remains uncertain, there are intriguing theories. One possibility is rooted in the idea that yawning may have evolved as a means for animals to protect the members of their tribe.

The exact reason behind why humans yawn is still a subject of scientific debate. Various theories attempt to explain this phenomenon. According to Douglas Parham, a speech scientist at Wichita State University, yawning might be a unique form of respiration. In moments of tiredness, when deep breaths become less frequent, yawning could serve as a specialized breathing mechanism, rapidly increasing oxygen intake while expelling excess carbon dioxide.

James Giordano, a neuroethicist and neuroscientist at Georgetown University, suggests that chemical changes in the body, such as a drop in oxygen or an increase in adenosine, could act as "yawn gates," triggering a yawn. By yawning, facial muscles compress, facilitating the flow of oxygen-enriched blood to the brain.

The purpose of yawning is further debated. Some propose that it cools the brain, while others believe it aids in stretching internal organs, invigorating the body. Despite yawning being a fundamental aspect of life, information on the topic is relatively sparse. Thomas Scammell, a neurologist at Harvard Medical School, notes that yawning is a primitive reflex shared among many animals and originating in the brain stem.

The contagious nature of yawning is another intriguing facet. Studies indicate that the likelihood of yawning increases sixfold after witnessing someone else yawn. James Giordano attributes this yawn contagion to social mirroring, where organisms instinctively imitate the actions of others. This behavior is not unique to yawning but extends to actions like scratching, leg crossing, and laughing.

Mirror neurons in the brain might be responsible for this mirroring behavior, as they match sensory experiences with physical actions. Research on social scratching in mice conducted by Zhou-Feng Chen at Washington University’s Center for the Study of Itch supports the idea that mimicking serves a purpose. When mice observed another mouse scratching itself, they promptly imitated the behavior, potentially saving energy and offering protection against diseases.

This mimicking behavior could extend beyond saving energy; it might also strengthen social bonds among animals. Thomas Scammell suggests that, similar to the way a friendly smile can elicit a reciprocal smile, yawns and other forms of imitative behavior may play a role in social communication, with more empathetic individuals being more prone to such social mirroring. As research continues, scientists aim to uncover the intricate reasons behind this seemingly simple yet fascinating act of yawning and its contagious nature.

Guided conversation questions: 

1. What surprised you the most about the information on yawning presented in the text?

2. Have you ever noticed that yawning seems to be contagious when you see someone else yawn? Why do you think this happens?

3. Do you agree with the various theories presented regarding the evolutionary purpose of yawning? Why or why not?

4. According to the text, yawning might be linked to tiredness and a decrease in deep breaths. Can you recall situations where you yawned due to tiredness or lack of deep breaths?

5. What are your thoughts on the proposed theories about the chemical changes in the body, such as a drop in oxygen or an increase in adenosine, triggering yawning?

6. The text mentions that yawning may serve different purposes, such as cooling the brain or stretching internal organs. Which theory resonates with you, and why?

7. How do you interpret the idea that yawning is a primitive reflex shared among many animals, originating in the brain stem? Do you think this has implications for human behavior?

8. Have you ever experienced a situation where you found yourself yawning after seeing someone else yawn? How do you think social mirroring, as discussed in the text, plays a role in this?

9. What are your thoughts on the concept of mirror neurons in the brain being responsible for imitative behavior, not only in yawning but also in actions like scratching, leg crossing, and laughing?

10. The text suggests that mimicking behaviors like yawning might serve a purpose in saving energy and offering protection against diseases. Can you think of other situations where mimicking behaviors could have similar benefits?