If people kissed with their eyes wide open and staring at each other, it would look, at the very least, creepy.
However, the reason why many people prefer to close their eyes during a kiss is not only the fear of scaring off their significant other.
According to a 2016 study published in the Journal of Experimental Psychology: Human Perception and Performance, people sometimes close their eyes to enhance their sense of touch.
Although the researchers did not link this feature to explain closed-eye kissing, it still applies in this context.
During the experiment, scientists attached special vibrating devices to the participants' hands and asked them to look at a screen with flashing letters.
Volunteers were asked to note the appearance of X and N symbols on the screen, and to report the presence or absence of vibration.
The researchers noticed that as the letter sequence became more complex, the participants became less able to feel the vibration.
To reiterate, although the experiment was not conducted with the purpose of studying kissing etiquette, its results can be adapted to this question.
Kissing can be called an intimate physical act. In order for the brain to fully appreciate the intensity and sensations, it is necessary to close the eyes - this way a person gets the opportunity to focus all his attention on the sense of touch and internal experiences.
