Asked by: Anonymous
Most people can’t focus on anything as close as a face at kissing distance so closing your eyes saves them from looking at a distracting blur or the strain of trying to focus.
Kissing can also make us feel vulnerable or self-conscious and closing your eyes is a way of making yourself more relaxed. It’s like turning out the light before having sex, but in miniature.
Read more:
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.