[nfb-talk] Study Finds Facial Expressions are Inherited
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Mon Dec 29 15:41:03 UTC 2008
Study finds facial expressions are inherited
Scientists have found that family members share a facial expression
"signature"-a unique form of the universal facial expressions encountered
In a rare study taking into account blind subjects, Gili Peleg, et al. have
discovered that family members were identified by their facial expressions
80% of the time, giving scientific support to the observation that a child
"has her Daddy's smile."
"Before our study, it was clear that there is a component of imitation that
influences facial expressions, but there was no study that compared the
of facial movements of relatives in several emotions," Peleg told
PhysOrg.com. Peleg is a PhD student supervised by Professors Eviatar Nevo
and Gadi Katzir
at the International Graduate Center of Evolution at the Institute of
Evolution, part of the University of Haifa in Israel.
In the 1970s-contrary to some views of the time but in accordance with
Darwin-psychologists Paul Ekman and Eibl Eibesfeldt showed that facial
are universal: people from different parts of the world smile when happy and
frown when sad, etc. Scientists also know that individuals have unique
expression signatures. Due to the existence of different nerves and muscles,
some people will have, for example, dimples, "Duchenne" smiles (with circles
under the eyes) and the ability to lift one eyebrow.
Wanting to know if there might be a heritable basis for these individual
signatures, Peleg et al. studied the gestalt of facial movements, seen in
such as the intensity and frequency of expressions.
"Facial expressions are non-verbal communication phenotypes, meaning they
are composed from genetics and
conditions," said Peleg. "We decided to investigate a population of
born-blind persons in order to eliminate the social influence and the
effects of imitation."
In the study, the scientists video-taped 51 subjects-21 who were blind, and
a total of 30 of their family members-when provoked to exhibit six emotional
states: concentration, sadness, anger, disgust, joy and surprise. Next, the
researchers used a classification tool to assign values (e.g. for types of
movements, frequencies) to each of the subject's expressions. After defining
the values, another classification tool determined which subjects were
Quite convincingly, 80% of the classifications correctly identified family
members when taking into account all six emotional expressions. The single
that received correct classification of family members when tested alone was
anger at 75%. In a test comparing the family members with each other, the
scientists also found that related subjects showed similar frequencies of
facial expressions for the emotions of concentration, sadness and anger, but
not the others.
"The hereditary influence that appeared in think-concentrate, sadness, and
anger may relate to the induction of the high diversity of facial movements
these emotions, as we found in a previous study," said Peleg. "We believe
that if our study population was larger, we could get significant results
in the other three emotional states: disgust, joy and surprise."
Peleg et al. hope that finding a heritable basis for facial expression
signatures may lead to discovering genes responsible for facial expressions.
it might be possible to develop repair mechanisms for people lacking facial
expressions, such as people with autism. Much information can be
through a person's facial expressions, and the scientists also wonder about
their evolutionary significance.
"Communication abilities have an evolutionary advantage; therefore facial
expression phenotypes should be conserved," said Peleg. "Facial expressions
important in inter-individual and hierarchical interactions of people within
our own species; between different human races; between different tribes;
and in animals between different species. The relationships of
mother-babies; bonding of pairs; aggression interactions between individuals
and so on should
be very important in hierarchical situations in human and animal societies.
Likewise, facial expressions should be of great importance as pre-mating
mechanisms between species.
"The genetic basis of facial expressions is probably composed of an array of
gene coding for muscle structure, bone structure and muscle innervations,"
Peleg continued. "However, our results also demonstrate kinship sequences of
facial expression. This could indicate genetic
and the existence of brain regions that control facial expressions."
Citation: Peleg, Gili, Katzir, Gadi, Peleg, Ofer, Kamara, Michal, Brodsky,
Leonid, Hel-Or, Hagit, Keren, Daniel, and Nevo, Eviatar. "Hereditary family
of facial expression." Proceedings of the National Academy of Sciences.
October 24, 2006. Vol. 103 No. 43. 15921-15926.
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