Kate Moss, George Clooney, Natalie Portman and Brad Pitt may be many people's ideas of dream dates. But pioneering research which combines economics and biology suggests they may not be perfect life partners.
According to a study to be discussed this month at a gathering of Nobel prize winners, 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 Autonoma de Madrid base their claims on the "prisoner's dilemma" model of behaviour, played out under laboratory conditions.
Two players were given the option of being a "dove" and co-operating for the greater good; or a "hawk" and taking the selfish option, with a chance of gaining more if the other player chooses "dove" and co-operates. 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, on August 23-27.
The explanation may be found in evolution. The two academics speculated that, on a subconscious level, people tended to view symmetrical physical attributes as a sign of good health and found people with them more attractive as a result.
Earlier studies suggested individuals with symmetrical faces tended to suffer fewer congenital diseases and therefore made better mating partners. As a result, the studies suggested, they were more self-sufficient and had less need for seeking alliances and the help of others.
"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," the pair said. "Through natural selection over thousands of years, these characteristics continue to the present day."
The authors also examined 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 suggested this was only partially true and testosterone could promote co-operative behaviour.
"Subjects exposed to higher levels of testosterone during fetal development did not co-operate less than the rest and even co-operated more than subjects with average levels. It seems thus that leading co-operation and not necessarily obtaining a higher individual profit are seen by some as a source of status."
The pair warned against jumping to the "simplistic conclusion" that facial asymmetry or testosterone could be used to predict a person's behaviour. But they suggested their research could be used to design public policies and as a corrective to purely economic-based decision-making.
"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."