:A S-confused1: Last updated at 8:16 AM on 11th June 2010 Comments (49) Men who fall instantly for a girl just because she looks gorgeous are usually accused of being shallow. But that, say scientists, is unfair. They are merely following their 'ancient' genetic preference to date pretty women and need only milliseconds to decide on a potential partner. Men go for a pretty face because it is a sign of fertility and the survival instinct draws them to women who can carry on their line, researchers say. All in the eyes: Men accused of being superficial are just following long-held survival instincts, say scientists Women, on the other hand, do not decide whether men will be a good partner on looks. Their survival instinct means they need to find out whether the man is committed, has a good personality and is a good provider. The findings come from a study by Professor Mark van Vugt and Dr Johanna van Hooff of the University of Amsterdam, and postgraduate student Helen Crawford from the University of Kent. They examined humans' bias towards looks by conducting a series of tests on 20 women and 20 men. The subjects were hooked up to a machine which recorded brain activity and were then given a task to perform. While they were doing the task they were shown a series of photographs of faces of the opposite sex, ranging from attractive to ugly. Men were easily distracted when they saw a pretty face but women stuck to the task. Professor van Vugt, whose study is to be published by the Oxford Journal, Social Cognitive and Affective Neuroscience, said that when men saw a face they were attracted to they made a snap judgment. 'Men definitely have the most wandering eye but it is because they have evolved to pay attention to cues of fertility and one of those cues is facial beauty - it's not that men are shallow,' he said. 'But we found they do make snap judgments about women much earlier than was previously thought. Of course men find a pretty face attractive but they make that decision on whether a woman would be a good mating partner in milliseconds.' The professor added that the findings showed that men's desire for beautiful women was part of evolution. 'This is something very ancient and a way of helping men find the best mate to produce children,' he said. He said women's brain activity was not affected when they were shown pictures of men while doing a task. 'Women were not distracted by attractive male faces because women need more proof of whether a man is a good mate,' he said. 'They make their decision much later than men.'