What all this means is that one special person can become chemically rewarding to the brain of another. Love at first sight, then, is only possible if the mechanism for generating long-term attachment can be triggered quickly. There are signs that it can be. One line of evidence is that people are able to decide within a second how attractive they find another person. This decision appears to be related to facial attractiveness, although men may favor women with waist-to-hip ratio of 0.7, no matter what their overall weight is. (This ratio may indicate a woman's reproductive health.)Another piece of evidence comes from work by a psychologist at Ben-Gurion University, who found in a survey that a small percentage (11%) of people in long-term relationships said that they began with love at first sight. In other words, in some couples the initial favorable impressions of attractiveness triggered love which sustained a lengthy bond. It is also clear that some couples need to form their bonds over a longer period, and popular culture tells many tales of friends who become lovers.