I was doing this little experiment on myself: Increase in pupil size. Came across it on tumblr, read up a little, and I kinda got interested! To be exact, my interest actually started when I was watching "Lie to Me" on my laptop last year. I was very fascinated by microexpressions, and one of them was the the increase in pupil size. Basically, microexpressions are facial expressions which are exhibited in micro-seconds, and they are very difficult to detect, unless you're a professional like Paul Ekman! For those interested, here's a little demo to test your skills on microexpressions: https://face.paulekman.com/face/default.aspx (It's located at the bottom right of the website, named "METT Demo".)