>>1267854All fetishes are the same so they are, in fact, easy to understand.
You see something you like and then one day a sexual event is tied with it in your memory. From then on every time you see it the image and feeling associated with it will be/can be strengthened. It doesn't have to happen but it can. Call it positive reinforcement, and since the modern world caters to any and all possibilities (hurray for the internet) we can have anything we want and thus our wishes/fetishes are easily fulfilled and reinforced.
It can be as simple as "I like headphones. Hey look, there's a girl who's wearing headphones. Hey, that's two things I like, girls and headphones! Awesome!" From then on the attachment grows.
