A group of Sardinian villagers has made a major contribution to solving the eternal debate about how much people's characters are determined by nature and nurture.
The 6,000 residents of four villages in a mountainous area of the Mediterranean island were volunteers in a study measuring the genetic component of 35 personality traits.
The study was carried out by the Cagliari section of the Italian National Research Council (CNR) and, according to the results, nature has won the argument.
The team found that genetic factors played a significant, but minor, role in determining whether a person develops a certain characteristic.
Environmental factors (such as the culture we live in and how we are brought up) and personal experiences were far more important, they said, having an influence of around 81%, compared to the 19% that is down to DNA.
However, the study showed that genetic factors had more sway over certain characteristics than others and that there are notable differences between sexes.
The tendency to be an extrovert, for example, is 20% determined by genetic factors in men, but 30% in women.
The same results were registered for neurosis - a female individual's propensity to be neurotic is 30% inherited from her parents, 10% more than a male's is.
The team, led by Antonio Cao of the CNR, carried out a series of psychological tests on the volunteers to establish how strong the 35 traits were in them.
They then compiled DNA profiles of each individual from blood tests and looked for correlations between genetic factors and any given characteristic.
The CNR chose the Sardinian villagers because they have so much in common with each other.
"Personality traits can be influenced by an enormous variety of factors," explained Cao.
"So the analysis is made simpler by studying the people of these relatively isolated communities, where there are fewer genetic and environmental differences".
The study has been published in US journal PLoS Genetics.
