Do you think of yourself as an extravert or introvert – or perhaps somewhere in between? Although the meaning behind these terms has shifted over time, we typically associate an extroverted person with being talkative and highly sociable, whereas introverts prefer quiet and are typically more reserved. But is there an underlying reason that explains human social behavior? Could these and many other personality traits originate in our genetic information, or do they form as a result of our environment and experiences? Perhaps they arise as a result of a mixture of the two. The popular field of epigenetics is just beginning to tackle the fascinating mystery of human personality and sociability, more recently in a new study published in the Proceedings of the National Academy of Sciences.
Researchers at the University of Georgia have discovered that an epigenetic mechanism is involved in silencing a gene that may control social behavior in people. Although the research is preliminary, it hints that epigenetics might play a role in determining whether someone can form healthy relationships or recognize others’ emotional states. What’s more, it could also help us understand diseases associated with impaired social ability.
The study demonstrates that methylation of a gene known as OXT could be connected to reduced sociability. OXT produces a well-known hormone called oxytocin that’s connected to a wide range of social behaviors. It has even been suggested that epigenetics and the oxytocin receptor gene could influence falling in love.
DNA methylation reduces the expression of genes, explained the study’s lead author, Brian W. Haas. Typically, an increase in methylation will result in a decrease in the gene’s expression, impacting its functioning. Haas is also an assistant professor of psychology at University of Georgia’s Franklin College of Arts and Sciences.
“When methylation increases on the OXT gene, this may correspond to a reduction in this gene’s activity. Our study shows that this can have a profound impact on social behaviors,” he said.
The research team collected saliva from over 120 people and assessed the level of methylation on the OXT gene via bisulfite conversion. They utilized a wide range of tests to measure their social skills and their brain structure and function to assess whether there was an association between DNA methylation and sociability.
They found that individuals who had a higher level of methylation on the OXT gene – which corresponds to suppressed gene expression – had greater difficulty recognizing the emotion behind particular facial expressions and were typically more anxious about their relationships with those they love.
For one test during the study, participants were shown short video clips of people’s faces, beginning with a neutral expression that slowly morphed into an emotional expression. The participant must hit a button as soon as they feel confident in naming the emotion.
“Participants with greater methylation of the OXT gene were less accurate in describing the emotional states of the people they saw in pictures,” Haas said. “That’s a typical characteristic associated with autism, for example.”
The team of scientists also used functional magnetic resonance imaging (fMRI) that measures brain activity via alterations to oxygenated blood flow. They were able to investigate the areas of people’s brains that were more active during certain tasks. Those with greater methylation of the gene demonstrated less neural activity in the regions of the brain connected to social-cognitive processing, such as the superior temporal sulcus. They also found that gray matter was reduced in the fusiform gyrus, an area of the brain that plays a key role in social cognition and face processing.
“All of our tests indicate that the OXT gene plays an important role in social behavior and brain function,” Haas concluded.
The research team cautions that their study offers only preliminary data regarding the association between DNA methylation of a particular oxytocin gene and human sociability. More research is necessary to precisely define oxytocin’s role and its genes.
“Methylation is a dynamic process, and level of methylation can change over the course of a person’s lifetime,” Haas explained. “But it may be possible to alter the level of methylation with some type of medication that could help people who have abnormalities in social cognition.” He has hopes that research on this topic may eventually progress the development of novel treatments and improve current ones for a vast range of social disorders.
Source: Haas, B.W., Filkowski, M.M., Cochran, R.N., Denison, L., Ishak, A., Nishitani, S., and Smith, A.K. (2016). Epigenetic modification of OXT and human sociability. PNAS.
Reference: University of Georgia. Silencing of gene affects people’s social lives, study shows. UGA Today. 20 June 2016.