[quote=@chukklehed]
Either way, if something can be taught, it can be learned by accident. Espers aren't given drugs or otherwise forced to manifest, so developing your power without help is more than just posible.
[/quote]

Actually, the artificial Espers are drugged, have stuff done to their brains, and get hit with all sorts of hypnosis stuff.

That's the Power Curriculum Programme. It's not actually something that is being taught, but scientific experimentation that modifies people to a point where they can obtain their own Personal Reality. That's why only Academy City had Espers. They had the scientific know-how.

[quote=Mikoto Misaka, Volume 1, Prologue]“Shut up. If you couldn’t bend a single spoon after having various crazy things done to you like have drugs injected directly into your blood vessels or have electrodes stabbed in through your ears and into the brain, what could it be but lack of talent?”[/quote]

That's how non-Gemstone Espers form.

Gemstones just happen to be ... monkey on typewriters.

[quote=SS2, Chapter 6]If a certain phenomenon has been caused artificially, then, as long as the same circumstances in the experiment are recreated in the natural world due to some factor or other, the same phenomenon will occur with no help from humans.[/quote]

That's why there's only fifty or so of them running around. Sogiita Gunha, Academy City's seventh-ranked Level 5, being one of them.

Oh yeah and Aisa, but she'll always be irrelevant compared to the guy who beats people up with an "Amazing Punch".