simple

there is a kind of inexplicable aura that when you first meet someone you can tell if they aren't completely there. when you first meet someone a 'little bit special' there's a strange knowledge that they aren't necessarily firing on all pistons. I think it's a human empathy thing, dating back from the days where people actually cared about each other. without knowing exactly why or how, you can see when someone has mental illness and this leads to immediately feeling sorry for them and wanting to help them with simple day-to-day tasks like filling a bowl with cereal or tying their shoelaces.

it's found in a slight vacancy or dullness behind the eyes, like all processes end at the cornea and behind only a slowly swirling void exists. it's sometimes a look of constant surprise that they have managed to remember to breathe. it can also be a real determined concentration on any very basic motor function.

JLS stands for 'Jack the Lad Swing'