Dr David Johnston, the leader of the study, said: "Blonde women are often depicted as being more attractive than other women, but also less intelligent.

"But it seems the association between blondes and beauty dominates any perception that they have low intelligence.

"This could explain why the 'blondeness effect' is evident in the marriage market."

Olga Uskova, president of the International Blondes Association, is quoted in the Mail on Sunday: "Blondes have wealthier husbands because we are more fun and outgoing, and men are more attracted to us.

"We also do better in the workplace because when we make a mistake we can say, 'Oh, sorry about that, it's because I'm blonde' and get away with it."