By 105 Student
People witness at an early age the phenomenon of contagious yawning. When one person in a crowded room yawns, it seems to trigger a chain reaction. Often times, friends will jokingly blame one another for passing on their yawn, like a contagion. For some reason, observing another person yawn makes you yawn. This same effect occurs when you see a person smiling or hear him laughing. Even subconsciously, you also will begin to smile. Yawning and laughing are both catching.
The premotor cortex initiates a person’s inadvertent reaction of laughing after hearing laughter. More specifically, a part of this area of the brain, called the PMVc area, helps trigger motor function in response to visual and auditory stimuli. It could also be the mechanism that makes you yawn when seeing others do it.
Researchers at the University College of London conducted a study to measure responses in the premotor cortex to certain sounds. Some sounds were considered negative, like the sounds of “retching,” while others were considered positive, like laughter. The researchers played the series of sounds for volunteers while observing their brains with an fMRI scanner. The premotor cortex showed stronger activity in response to the positive stimuli than to the negatively associated noises. Laughter is often shared between friends, and it helps people to form bonds with one another. It establishes emotional closeness, even if just for a moment. These aspects of laugher could explain its positive association.
Yawning has also been linked to emotional closeness. In a study published in 2011, the yawning patterns between people who were considered to have a close social bond (as friends or family) and between people who were strangers. Participants were observed for a time period between 6 minutes to 2 hours, and each yawning episode was recorded. All circumstantial aspects were noted, and the responses of others who sensed the yawn were recorded. Those who were related responded to the other person’s yawn (by yawning) much more quickly and more often than they did responding to a stranger’s.
A simple “mirroring” action could explain the contagious effects of laughter and yawning. Humans and animals are actually hardwired to demonstrate this mirroring effect. Mirror neurons are found in parts of the human brain designated to motor function, like the premotor cortex, and are the neurons that trigger responses in the premotor cortex to stimuli. They are known as the human Mirror Neuron System (hMNS).
Mirror neurons were first discovered in Monkeys. In the 1981 study, these cells showed strong signs of activity both when the monkey itself was acting and when observing a peer mimic the same action. Mimicking an action is the brain’s way of trying to understand the physical action itself through replication, and can help people relate to one another’s behavior.
Van Overwalle and Baetens assert there is yet another brain system involved in contagious laughter and yawning. The mentalizing system in the prefrontal cortex works with the mirroring system to process why the behavior is taking place. This is crucial to human interaction because it helps to establish empathy and encourage social bonding, which also promotes the mirroring effect (http://www.ncbi.nlm.nih.gov/pubmed/19524046).
The premotor cortex, hMNS, and mentalizing system are all linked in responding to visual and auditory stimuli. Their responses are more strongly triggered in the premotor cortex when a person interacts with someone he or she is close to. It may be instinct to mirror someone’s yawn or laugh due to the hMNS, but when two people have an emotional tie, the mentalizing system factors in to facilitate understanding and improve the relationship between them. Next time a friend tries to point a finger at you for spreading the yawning bug, know he or she is really just an affectionate fool for you.