Copulins are a series of fatty acids produced by the vagina at the peak of ovulation, reducing a man's abiltiy to judge women by their looks alone. This is an important aspect of female attraction considering that looks are the primary attraction swtich or trigger for males

Copulins

According to Vienna University biologists, Karl Grammer and Astrid Jütte, copulins block a man’s ability to judge a woman’s attractiveness by the way she looks and the sound of her voice.

These chemicals attract the man to a woman -- even if the man might not have otherwise been interested in the woman on the basis of her looks or the sound of her voice.

Grammer and Jütte conducted a study, wherein they exposed 66 men (unknowingly) to copulins. They then showed them pictures of women and asked them to rate the attractiveness of each woman. They rated all the women as being significantly more attractive to them than when they were when exposed to ordinary water (i.e., no copulins). The interesting thing was that the less attractive the woman was rated prior to the men's exposure to copulin, the bigger the rise in their perceived attractiveness after exposure. Curiously enough, when copulins were introduced, plainer-looking women scored higher marks than attractive women! The smell of copulins seems to makephysical attractiveness less important for men.

When optimized, copulins have demonstrated that they bring about a testosterone surge in men up to 150% of baseline, thereby causing a man to have a heightened desire to copulate. They also release neurotransmitters that directly modify men's behavior, such astriggering sexual excitement.