Facial expressions appear to be at least partially inherited, according to a study of blind people and their relatives.
Experts say the findings indicate that people do not always learn their expressions for certain emotions by copying the facial quirks they see as youngsters.
To understand the “nature vs. nurture” component of facial expressions, Israeli researchers recruited 21 people who were born blind along with 30 of their relatives. The 51 volunteers were videotaped as they recounted happy, sad and aggravating life experiences, concentrated on puzzles and heard a gory story and an unexpected question in gibberish.
Scientists then analysed these hour-long sessions, noting each individual change – such as raised eyebrow or pursed lips – that occurred in subjects’ faces as they felt various emotions. The team entered the information into a computer, which analysed the sequences and frequencies of these facial movements using a sophisticated statistical program.
According to the analysis, the blind participants were significantly more likely to make angry, sad and pensive facial expressions that resembled those of their relatives than of strangers.
This result was striking given that the blind subjects had never seen their relatives at all, says Gili Peleg at the University of Haifa, Israel, one of the scientists behind the new research.
One subject did not even know his biological mother until the age of 18 years because she had given him up for adoption at birth, Peleg adds. “When we saw the similarity between their expressions it was just amazing,” she says.
“I think it’s very surprising,” says facial expression researcher Anthony Little at the University of Stirling, UK. “The findings imply that genetics might be involved.”
Peleg speculates that genes might influence the muscle and nerve structure in the face. This, in turn, would create biological constraints that make facial expressions more similar among relatives.
Scientists say that the similarity in facial expressions among relatives could perhaps have an evolutionary basis. “Family resemblance in expressive styles probably has adaptive value to the individuals in order to recognise kin from non-kin,” says David Matsumoto at San Francisco State University in California, US.
Peleg notes that for three facial expressions of the blind participants in her study – joy, surprise and disgust – the resemblance to relatives and strangers was not significantly different. She says that this might be because these expressions are for some reason more universally similar and not as prone to genetic variations.
Journal reference: Proceedings of the National Academy of Science (DOI:10.1073/pnas.0607551103)