Note: this entry was previously published on Octopractical.
It was a beautiful day at the White Oak Pavillion at Mt. Pisgah in Eugene, OR. The sunshine was filtering through the light green usnea lichen that hung from the stately oaks. The sky was the deep blue of Fall. It’s no wonder that the Pavillion is one of Eugene’s top three spots for a wedding. But on this day, those gathered here were considering love from a different point of view.
Dr. Sarina Saturn, an assistant professor of psychology at Oregon State University, presented her work on the oxytocin receptor, OXTR, as a keynote speaker for the University of Oregon Institute of Neuroscience’s annual retreat. Oxytocin has a reputation as the “love molecule” and is one of the superstar molecules of neuroscience- a neurotransmitter like serotonin an dopamine that has debuted in the public consciousness as a molecule of positive psychology. Oxytocin is actually both a hormone and a neurotransmitter. It can act as a signalling molecule for both neuronal tissue, as in the brain, and non-neuronal tissue, such as the uterus. It is produced in abundace in prarie voles, a species that forms near-monogamous pair bonds. It is causes uterine contractions during labor, and is thought to carry that powerful first flush of love between a mother and an infant. It is also know to have a role in the stress response, inhibiting cortisol production.
Unlike many other neurotransmitters, there is only one receptor for oxytocin present in the human genome. It is on the third chromosome. But not everyone has exactly the same form of OXTR. It is mostly the same, except that at one location within the molecule, some individuals have an adenine nucleotide (or “A” of the famous four: A, T, G and C) and others have a guanine (or “G”). This is what is known as a single nucleotide polymorphism, or SNP (pronounced “snip”). Since we all have two copies of the third chromosome, we each have two versions of the genetic code for the oxytocin receptor. We can have either two A’s (about 25% of us), and A copy and a G copy (about 50% of us), or we can have two G’s (about 25% of us). This is one of the many points at which we humans have natural genetic variation.
Dr. Saturn is a molecular biologist turned social psychologist. She did her Ph.D. work in the lab of Joseph LeDoux, author of The Synaptic Self. At that time, she worked on the amygdala- the so-called emotional center of the brain. But her career now focuses on the SNP of the oxytocin receptor in humans- and her findings point to the big role of this little difference between us. She and her colleauges have found that this single neucleotide substitution has a role in how we behave both in reaction to stress, and in situations where we need to be empathetic and “read” the emotions of others through body language. Those of us with the GG genotype are better at reading the intentions of other people by just looking at picutre of the eyes than those of us with one or two A’s. In addition, people with a GG genotype report feeling more empathy than their AA or AG peers. People with two G’s are also better able to keep calm when anticipating a stressor.
In another study, Dr. Saturn and her colleauges found that a GG genotype does not just impact how empathetic a person feels. It also manifests in the person’s behavior in a way that can be observed by others. The researchers recorded conversations between romantic partners. In particular, they recorded the behavior of one partner with he or she was listening to thier romantic partner talk about a difficult time in thier lives. This show of vulnerability is thought to consistently elicit an empathetic, prosocial reaction. The researchers then showed the videos of the listeners to another group of people, who ranked the listener’s empathy based on viewing only twenty seconds of the listener’s behavior. Judges rated listeners with a GG genotype as signifcantly more empathetic and prosocial than listeners with AG or AA genotypes.
“At this point, I cried for days,” said Dr. Saturn when relaying these results, “and not because I knew I would have get some cool papers out of it. I genotyped myself and I am an AA.”
But the story with oxytocin is not yet over. There is some evidence that intranasal administration of oxytocin- in addition to increasing eye-gaze and feelings of empathy towards those present, can also promote exclusionary behaviors of those in the out-group, such as ethnocentrism. There is likely some social advantage to being a carrier of the A alelle of the OXTR, net yet uncovered by research. I wonder if this is what Dr. Saturn will investigate next.
S.M. Rodrigues,*, L.R. Saslow, N. Garcia, O.P. John, D. Keltner. (2009) An oxytocin receptor genetic variation relates to empathy and stress reactivity in humans. Proceedings of the National Academy of Sciences, 106: 21437-21441. (*co-first author)
A. Kogan, L.R. Saslow, E.A. Impett, C. Oveis, D. Keltner, S.R. Saturn. (2011) Thin-slicing of the oxytocin receptor (OXTR) gene and the evaluation and expression of the prosocial disposition. Proceedings of the National Academy of Sciences, 108: 19189-19192.