Between 40-60% of people find yawning contagious, but the reason why was unclear. Finnish scientists found that the periamygdala sections of the brain become inactive when people witness someone else yawn, suggesting that certain parts of the brain are responsible for a person’s perception of a yawn. Other theories suggest that yawning evolved as a way to signal sleep schedules and danger. Further research is needed to fully understand this behavior.
Most people, when they see someone else yawning, quickly feel the urge to yawn as well. Between 40 and 60 percent of people automatically find yawning contagious and yawn. The standard answers from scientists as to why people find yawning contagious were that while it was clearly a real phenomenon, there was no obvious reason for it. Research conducted in 2005 by Finnish scientists, however, may point to certain parts of the brain as being responsible.
When a person witnesses someone else yawn, they have a mostly unconscious urge to do the same. People may become aware of the urge, but scientists suggest that the initiation of the urge to yawn is unconscious. This means that the signal must bypass the mirror neuron system, a process that would make this response a conscious, imitative act. Scientists have often in the past suggested that the mirror neuron system causes yawning.
Instead, the researchers found that seeing someone else yawn appears to cause the periamygdala sections of the brain to become inactive. This is a small part of the brain on either side of the head that helps interpret things like facial expressions. If that worked, the conscious response to the yawn might be, “Oh, he’s tired.” By temporarily blocking this reading, however, the response cannot at first be a conscious perception.
This doesn’t specifically explain why people find yawning contagious, but it does suggest that there are sections of the brain responsible for a person’s perception of a yawn. Furthermore, the answer does not start with the mirror neuron system, but bypasses it.
Other explanations include the idea that yawning may have evolved in early man as a way to signal or set sleep schedules. An infectious yawn meant that perhaps more than one person was tired and people needed to sleep accordingly. Since tiredness could indicate a less energetic response to danger, yawning would mean that people would have to find shelter and get out of harm’s way. Those who yawned and paid attention may have been selected in the species because they got adequate sleep and were more alert to danger.
The exact mechanism and reasons people yawn in response to others are not yet clearly understood. Research from 2005 may point the way to looking for further clues about this interesting and automatic human behavior.
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