People with symmetrical faces are more self-sufficient and less likely to co-operate, new research suggests

Kate Moss, George Clooney, Natalie Portman or Cristiano Ronaldo may be many people's ideas of dream dates, but pioneering research that combines economics with biology suggests they may not be perfect life partners.

According to a study to be discussed this month at a gathering of Nobel prizewinners, people blessed with more symmetrical facial features, which are considered more attractive, are less likely to co-operate and more likely to selfishly focus on their own interests.

Santiago Sanchez-Pages, who works at the universities of Barcelona and Edinburgh, and Enrique Turiegano, of the Universidad Autónoma de Madrid, base their claims on the "prisoner's dilemma" model of behaviour, played out under laboratory conditions. Two players were each given the option of being a "dove" and co-operating for the greater good; or a "hawk", taking the selfish option, with a chance of gaining more if the other player chose "dove" and co-operated. The subjects' faces were then analysed.

The study found that people with more symmetrical faces were less likely to co-operate and less likely to expect others to co-operate. The findings will be presented at the annual Nobel Laureate Meetings in Lindau, Germany, from 23 to 27 August.

The explanation may be found in evolution. The two academics speculate that, on a subconscious level, people tend to view symmetrical physical attributes as a sign of good health and find people with them more attractive as a result. Earlier studies have suggested that individuals with symmetrical faces tend to suffer fewer congenital diseases and therefore make better potential mating partners. As a result, the studies suggest, they are more self-sufficient and have less need for seeking the help of others.

The pair write: "As people with symmetrical faces tend to be healthier and more attractive, they are also more self-sufficient and have less of an incentive to co-operate and seek help from others. Through natural selection over thousands of years, these characteristics continue to the present day."

The authors also examine the relationship between co-operation levels and exposure to testosterone during development. Testosterone is usually associated with aggressive behaviour, suggesting "alpha males" do not make great team players.

But the authors suggest this is only a partial truth and that testosterone can promote co-operative behaviour. They write: "Subjects exposed to higher levels of testosterone during foetal development did not co-operate less than the rest and even co-operated more than subjects with average levels. It seems that leading co-operation and not necessarily obtaining a higher individual profit are seen by some as a source of status."

The pair warn against jumping to the "simplistic conclusion" that facial asymmetry or testosterone can be used to predict a person's behaviour, but they suggest their research could help to design public policies and act as a corrective to purely economic-based decision making.

They note: "If certain behaviours such as smoking, drinking or high-speed driving are perceived by those who engage in them as part of their quest for status, it is very unlikely that providing economic disincentives like higher taxes, prices or fines will have a strong deterrent effect."