Is genuine interest in the subject matter enough?

I may be jaded, but IMO having a "genuine interest" in math would already put you in the 99th top percentile of the population. This might not be as good as being "gifted" (whatever that means), but it should at least be close enough for a rationality camp.

Edited to add:

DISCLAIMER: I myself have never been through the rationality camp, so I'm just guessing here.