Take a look at the two images below. Which version of the photo seems more attractive to you? Don’t spend too long thinking about it, just go with your gut.
Most prefer the picture on the right but can’t say why.
This experiment has been repeated with various groups and, regardless of the gender and sexual orientation of the participants, the results are usually the same.
The difference between the pictures is that the right-hand one has been digitally altered to have slightly more dilated pupils. That is it.
As Dale Carnegie pointed out almost 100 years ago in his timeless book How to Win Friends and Influence People, we take an interest in people who like us. Further, researchers have found that when we are looking at something that interests and excites us our pupils expand while when we see something boring our pupils contract.
Our brains pick up on all kinds of subtle physical cues like this to help us determine how others feel about us. This is why pretending to be interested in people in an attempt to manipulate them generally doesn’t work; they will likely pick up on your insincerity on an unconscious level.
Thus, finding just one thing about someone that really interests you and focusing on that thing while you interact with them may, paradoxically, make them more interested in you.