I wrote an article on NLP and visual accessing cues that got a lot of positive feedback from readers. I thought I would write another quick article on the eyes. This is about a cool little thing you can try out with anyone.
Simply put; when we see things we like, our pupils dilate in order to take in more light, and so that we can also better see what we are looking at. When our pupils dilate, we are also looking at a person, picture, or object more closely; which causes the pupil-dilation (exactly like a camera lens). A book on dating or attraction my tell you that pupil dilation is a sign of attraction, and it is, but this is not always the case.
The study of pupil size is called pupillometrics. And there have been all sorts of studies done on the subject, you can probably try out a few with your friends! A hungry person's pupils will dilate when they are shown food. A woman's pupils will dilate when shown pictures of a child. A ornithologist's eyes will probably dilate if you show them a picture of a bird.
This is one of the reasons poker players wear sunglasses. See a hand you like, and your eyes are going to give you away without you even knowing what's happening. There are of course false tells. Many types of mushrooms will cause your pupils to dilate, and in the past people would eat certain strains to appear more attractive; as big pupils do not only mean attraction, but also may case somebody to reciprocally feel attracted to somebody whose looking at them with dialed eyes. Whoa, talk about behavior that is hardwired into our brains. Although I wouldn't say that this is an effective strategy for card playing...