It's really odd in a work situation, when you mention an idea to a cow orker, they don't get it at first, so you explain it to them a little more slowly, they still don't get it.

Then a little while later the penny will drop and they'll suddenly figure it out and think they came up with the idea all by themselves, usually coming back to you and going "hey I've got this great idea! Wanna hear it?".

I guess it happens to most people, in both roles, at various times, though.