Genes play a greater role in forming character traits - such as self-control, decision making or sociability - than was previously thought, new research suggests.
A study of more than 800 sets of twins found that genetics were more influential in shaping key traits than a person's home environment and surroundings.
Psychologists at the University of Edinburgh who carried out the study, say that genetically influenced characteristics could well be the key to how successful a person is in life.
The study of twins in the US - most aged 50 and over- used a series of questions to test how they perceived themselves and others. Questions included "Are you influenced by people with strong opinions?" and "Are you disappointed about your achievements in life?"
The results were then measured according to the Ryff Psychological Well-Being Scale which assesses and standardises these characteristics.
By tracking their answers, the research team found that identical twins - whose DNA is exactly the same - were twice as likely to share traits compared with non-identical twins.
Psychologists say the findings are significant because the stronger the genetic link, the more likely it is that these character traits are carried through a family.
Professor Timothy Bates, of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, said that the genetic influence was strongest on a person's sense of self-control.
Researchers found that genes affected a person's sense of purpose, how well they get on with people and their ability to continue learning and developing.
Professor Bates added: "Ever since the ancient Greeks, people have debated the nature of a good life and the nature of a virtuous life. Why do some people seem to manage their lives, have good relationships and cooperate to achieve their goals while others do not? Previously, the role of family and the environment around the home often dominated people's ideas about what affected psychological well-being. However, this work highlights a much more powerful influence from genetics."
The study, which builds on previous research that found that happiness is underpinned by genes, is published online in the Journal of Personality.