A guy I like always flirts with me and always tries to get my attention. When I speak, walk, talk to friends, laugh, or even when I'm quiet. Sometimes I think he likes me but then like a stupid girl I am I over think it.
So with the pupil dilation they say they dilate and get big when you look at the person you like. However, his don't dilate. Or I tried looking today but I couldn't really tell.
It's not a matter of belief; it's scientific fact. When you have feelings for someone (especially someone new in your life), you get excited, your heart-rate increases, and your pupils dilate. The dilation is what causes that "gleam/twinkle in your eye" because light will reflect off of the cornea.
Certainly, HOW MUCH someone gets excited will vary, depending on the person, and depending on how they feel for the other person, but some difference can be detected in just about everyone, at least with instruments.
How pupil dilation works for dating: pupil dilation happens when the heart beats faster or during a stressful situation. So when a guy looks at you and you make him nervous his pupils will dilate noticeably. It's a great thing to find a guy that has this reaction to you.