system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we raise our hands when we get excited; and for that matter, why do we clap? Is this the result of some kind of evolutionary process?
gpt
Clapping isn't a reflex -- it's something you are taught to do. Likely, the same goes for this hand raising thing.

Why does it happen? Probably because people like to do what is expected of them. (Or, what they expect is expected of them.)