PARIS — The human capacity to read the emotions of others does not depend solely on our education and experiences. It is also influenced by our genes, according to a major international study published in the journal Translational Psychiatry. When it comes to empathy, in other words, we don't all start off with the same innate abilities.

Nor is there one objective measure of empathy. The scientists involved in the study, therefore, based their research on a "quotient of empathy" as gaged in a questionnaire developed in 2004 at the University of Cambridge. Researchers from France's Université Paris-Diderot, Institut Pasteur and Centre National de la Recherche Scientifique (CNRS), the national research body, also participated in the study, which focused on 46,000 clients of the genetic analysis company 23andMe.

The "quotient" measures two types of empathy: cognitive, which means recognizing the feelings of others; and affective, which is about making an adapted emotional response. Participants completed the questionnaire online and provided a saliva sample. Comparing the data, researchers found that at least one 10th of the variation of the feelings of kindness, compassion and caring depends on our DNA. They also demonstrated that women, on average, are more empathic than men.

A newborn macaque imitates tongue protrusion — Photo: Evolution of Neonatal Imitation/Wikipedia

Several months ago, another University of Cambridge study came to the same conclusion. Researchers looked at so-called "eyes tests' carried out on 89,000 people to gauge emotional responses — empathy, in other words. By dissecting the findings further, they may have even identified one of the genes responsible for the variability: LRRN1 (leucine-rich repeat neuronal protein), which exists in several variants, some of which, found among women, seem to be correlated to a better perception of emotions. What's more, LRRN1 is very active in a part of the brain called the "striatum," which imaging has proved to be very involved in decision-making and cognitive empathy.

Scientists are especially interested in LRRN1 and other possible gene influencers because of disorders like autism, which is characterized by a difficulty identifying what others feel.

Going into the study, the researchers predicted that in the case of autistic subjects, they would see a genetic profile that is less favorable to the development of empathy. And in fact, that's exactly what they did find, according to geneticist Thomas Bourgeron, a Université Paris-Diderot professor who co-authored the study. What they weren't able to determine, however, is which — if any of the 12 susceptible genes they focused on — has a decisive influence in the predisposition to empathy. "They all probably contribute a little," Bourgeron says.

Nor is empathy linked to a single part of the brain, according to research done by neurosurgeon Hugues Duffau, who has revolutionized his discipline by operating on people's brain tumors while they're awake. Empathy is instead linked to a set of zones, each of which plays a role, he found.

One 10th of the variation of the feelings of kindness, compassion and caring depends on our DNA.

Duffau is interested in "mentalization," a concept neuropsychologists use to designate the ability of individuals to understand themselves and to understand relationships with others in terms of mental states. He found that mentalization is not controlled by a particular region of the cortex, but by networks of diffused and interconnected neurons.

One family of neurons in particular — so-called mirror neurons — is essential in understanding others. In the 1990s, Italian researchers working with neuroscientist Giacomo Rizzolatti made a staggering discovery by studying what happens in a monkey's brain when it observes an action. Its motor neurons, which control the body, kick into gear — just as they would if the monkey were repeating the action, rather than just observing it. It's as if by looking at someone act, the monkey feels itself acting. It sees itself in the other, as in a mirror.

Roy Mukamel of the Laboratory of Cognitive Neurophysiology of Los Angeles, in the United States, believes that human have mirror neurons as well, and that they play a key role in cognitive processes such as the understanding of emotions or learning by imitation. These mirror neurons may also be linked to the phenomenon of emotional contagion or mass hysteria.