One study found that when a male rat was injected with testosterone, the female rat immediately swarmed. Men with high levels of androgens stimulate women's instincts even when they are silent. Since humans are also animals, they affect the "instinct of leaving offspring" that women have. In other words, women are instinctively attracted to men who have high levels of testosterone. Women unknowingly choose healthy and strong individuals. DNA knows that if you can choose a man with a good gene, it will be easier to prepare a child-rearing environment. Many women say that they like gentle and strong men, but it can be said that hormones have an effect on the popularity of men with large vessels. Testosterone is a hormone that enhances "masculinity". As the amount of testosterone secreted increases, the body becomes better and the hair becomes thicker, resulting in a masculine appearance. It is also the function of testosterone to promote the improvement of fighting spirit and motivation, and to enhance the ability to work energetically. Men with high testosterone levels are full of strength, so they are always energetic for work and private life, and have a strong spirit of challenge.