Did you know, that people act differently when they're being watched?
For an example, my brother. When he is playing games, he sits quietly and normally and holds the controller the way it has to be. But when our mother tells him his playtime is over, he starts to jump when he's fighting and saying 'oooh' and 'aaah'.
Or maybe when you're at school, and you're in front of your crush. You start acting differently, don't you? You act more... sophisticated, giggle nervously sometimes. I mean, if you're a girl. If you're a boy, don't you act tough in front of the girl you like? Or more... mature?
Or when you lie. When you look a person in the eye and say "I don't know what you're talking about" when you do, don't you talk differently? Or maybe feel your mouth being... heavier? And you have to fake a laugh?
Or when you're just being watched, like, by a teacher you want to impress. Don't you make unusual moves, such as you don't regularly?
I have almost all the proof I need here. Also, people start shuffling their feet, looking around nervously, starting to sweat, or don't know anything when being actually watched. How did I get that idea?
Just by watching you.