Genetics of oxytocin

The sensitivity to oxytocin in humans is partlygenetically determined.

Oxytocin receptor polymorphism
The oxytocin receptor in humans has several alleles, which differ in their effectiveness. Individuals homozygous for the "G" allele, when compared to carriers of the "A" allele, show higher empathy, lower stress response, as well as lower prevalence of autism and of poor parenting skills.

Everyday identification of the gene
It has been experimentally confirmed in a University of Toronto study that human subjects observing the way others listened to people can predict the presence of the genetic variant.

In the study 23 couples were filmed describing a moment of personal suffering while their partner listened. Subjects then watched a 20 second silent recording of the exchange and scored the listener for their "prosocial traits", such as a nurturance or empathy.

The people with GG alleles were identifies to be more prosocial than people with the AG or AA variant. The effect was marked: of the top 10 most trusted people, 6 were GG; while of the 10 least trusted people, 9 had at least one copy of A.