Seriously? They are getting excited by a hyper-stimulus. Women generally have an instinct to find a guy attractive if other women find him attractive. Older women have enough experience to see how this instinct can lead them astray and don't need the release or have the energy levels so they control it better. The people who produce these teen phenomena understand the psychology very well and choose/package their product carefully and present them to the audience as already popular.
It's sort of like picking yourself up off the ground by pulling on your shoelaces but it works a treat and the money rolls in.
I really have NO IDEA 😆 I'm a fan of one direction, but hell I wouldn't scream like that if I see them !! Its INSANE !! I know it can be REALLY existing, but it still doesn't mean that I would lose my voice at a concert 😆 the poor guys must deal with all that crap 🙉