Have you ever noticed that one yawn sets off a chain reaction, spreading to others nearby? Dr. Gordon Gallup and colleagues at the University at Albany – State University of New York believe that rather than being a precursor to sleep, yawning is designed to help us communicate.
Yawning is a universal, involuntary action, lasting an average of six seconds. Babies yawn in the womb, and most animals do it too. Gallup suggests that the purpose of yawning is to share information within our social group.
Gallup has spent years exploring the phenomenon of contagious yawning. He defines it as “the onset of a yawn triggered by seeing, hearing, reading, or thinking about another person yawn.”
While it’s uncertain what causes contagious yawning, it may have developed early in human history. One yawn may have led to others to help groups of early humans avoid being attacked by predators.
“During human evolutionary history when we were subject to predation and attacks by other groups, if everybody yawns in response to seeing someone yawn, the whole group becomes much more vigilant, and much better at being able to detect danger,” Gallup said.
Only about half of adult humans are prone to contagious yawning. In his tests, Gallup found that susceptibility to contagious yawning is linked to people’s success on a face recognition task. Those who are more susceptible score lower on a measure of schizotypal disorder, a personality disorder characterized by a need for social isolation.
Gallup’s later studies used functional MRI, or fMRI, to view subjects’ brains as they watch another person yawning. He found that this experience triggers “unique neural activity” in areas which play a role in self-processing, such as autobiographical memory. “Our findings provide further support for the hypothesis that contagious yawning may be part of a neural network involved in empathy,” his team concludes.
Dr. Catriona Morrison and a team of researchers from the University of Leeds in the United Kingdom came to a similar conclusion. “We believe that contagious yawning indicates empathy,” she said. “It shows an appreciation of other people’s behavioral and physiological state.”
To test this idea, Morrison’s team placed volunteers in a room with a researcher who yawned ten times in ten minutes. The number of times the volunteers yawned in response was recorded and compared with their empathetic skills, which were tested by deducing emotions from pictures of eyes.
Those who succumbed most to contagious yawning were the individuals who scored higher on the empathy test. Psychology students scored significantly higher on empathy and yawned more often than engineering students. On average, the psychology students yawned 5.5 times in response, while the engineering students yawned only 1.5 times.
“We worked with psychologists because they are widely regarded to be more empathetic and engineers because they are often seen as ‘systemizers’, who are more interested in objects and functions than people,” said Dr Morrison. “We found the psychologists yawned contagiously more than the engineers. It means they are further along the socialized spectrum. They have more social awareness.”
Yawning also may help modulate core body temperature. Gallup’s team examined available medical and biological evidence which could indicate that yawning is a thermoregulatory mechanism, carried out to keep body temperature within correct limits.
The evidence is supported by a finding that people with multiple sclerosis, migraine headaches, epilepsy, stress and anxiety, and schizophrenia often show “atypical yawning patterns.” These disorders have also been linked to problems with thermoregulation. Drowsiness also causes a change in body temperature.
Gallup G. G. et al. Yawning and thermoregulation. Physiology and Behavior, published online May 13, 2008.
Platek S. M., Mohamed F.B. and Gallup G. G. Contagious yawning and the brain. Cognitive Brain Research (2005) Vol. 23, pp. 448-52.
Platek S.M. et al. Contagious yawning: the role of self-awareness and mental state attribution. Cognitive Brain Research (2003) Vol. 17, pp. 223-27.
Dr. Morrison’s research was presented at the British Association’s Festival of Science held at the University of York from September 9-15, 2007.