May
not be linked to empathy after all
While
previous studies have suggested a connection between contagious yawning and
empathy, new research from the Duke Center for Human Genome Variation finds
that contagious yawning may decrease with age and is not strongly related to
variables like empathy, tiredness and energy levels.
The
study, published March 14 in the journal PLOS ONE, is the most
comprehensive look at factors influencing contagious yawning to date.
The
researchers said a better understanding of the biology involved in contagious
yawning could ultimately shed light on illnesses such as schizophrenia or
autism.
Contagious
yawning is a well-documented phenomenon that occurs only in humans and
chimpanzees in response to hearing, seeing or thinking about yawning. It
differs from spontaneous yawning, which occurs when someone is bored or tired.
Spontaneous yawning is first observed in the womb, while contagious yawning
does not begin until early childhood.
Why
certain individuals are more susceptible to contagious yawning remains poorly
understood. Previous research, including neuroimaging studies, has shown a
relationship between contagious yawning and empathy, or the ability to
recognize or understand another's emotions. Other studies have shown
correlations between contagious yawning and intelligence or time of day.
Interestingly,
people with autism or schizophrenia, both of which involve impaired social
skills, demonstrate less contagious yawning despite still yawning
spontaneously. A deeper understanding of contagious yawning could lead to
insights on these diseases and the general biological functioning of humans.
The
current study aimed to better define how certain factors affect someone's
susceptibility to contagious yawning. The researchers recruited 328 healthy
volunteers, who completed cognitive testing, a demographic survey, and a
comprehensive questionnaire that included measures of empathy, energy levels
and sleepiness.
The
participants then watched a three-minute video of people yawning, and recorded
the number of times they yawned while watching the video.
The
researchers found that certain individuals were less susceptible to contagious
yawns than others, with participants yawning between zero and 15 times during
the video. Of the 328 people studied, 222 contagiously yawned at least once. When
verified across multiple testing sessions, the number of yawns was consistent,
demonstrating that contagious yawning is a very stable trait.
In
contrast to previous studies, the researchers did not find a strong connection
between contagious yawning and empathy, intelligence or time of day. The only
independent factor that significantly influenced contagious yawning was age: as
age increased, participants were less likely to yawn. However, age was only
able to explain 8 percent of the variability in the contagious yawn response.
"Age
was the most important predictor of contagious yawning, and even age was not
that important. The vast majority of variation in the contagious yawning
response was just not explained," Cirulli said.
Because
most variability in contagious yawning remains unexplained, the researchers are
now looking to see whether there are genetic influences that contribute to
contagious yawning. Their long-term goal in characterizing variability in
contagious yawning is to better understand human diseases like schizophrenia
and autism, as well as general human functioning, by identifying the genetic
basis of this trait.
"It
is possible that if we find a genetic variant that makes people less likely to
have contagious yawns, we might see that variant or variants of the same gene
also associated with schizophrenia or autism," Cirulli said. "Even if
no association with a disease is found, a better understanding of the biology
behind contagious yawning can inform us about the pathways involved in these
conditions."
Cirulli
authored the study, which was funded by National Institute of Mental Health
(K01MH098126) and the Ellison Medical Foundation New Scholar award
(AG-NS-0441-08), with Alex J. Bartholomew, also of the Duke Center for Human
Genome Variation.
Story Source:
The
above story is based on materials provided by Duke Medicine. Note:
Materials may be edited for content and length.
Journal Reference:
1.
Alex J. Bartholomew,
Elizabeth T. Cirulli. Individual Variation in Contagious Yawning
Susceptibility Is Highly Stable and Largely Unexplained by Empathy or Other
Known Factors. PLoS ONE, 2014; 9 (3): e91773 DOI:10.1371/journal.pone.0091773
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Duke Medicine. "Contagious yawning a mystery: May not be
linked to empathy after all." Science
Daily, 14 March 2014.
<www.sciencedaily.com/releases/2014/03/140314211843.htm>.