Kissing is both pleasant and healthy, no doubt. But many scientists are still trying to answer the question why most people close their eyes when kissing. Here is what Singaporean scientist Yau Che Ming, a professor at the National Education Institute, thinks about that.

One of his theories suggests that we close our eyes to ease strong emotional pressure we experience when kissing. While it’s common to think that kissers close their eyes to escape from reality and to focus on their affectionate feelings. Another theory of the scientist goes about a person’s visual perception of his or her partner. Being so close, we either can’t see the face of our lover clearly, or we get it too clear. That visual perception often triggers unpleasant sensations and we close our eyes for protection.