I’m in the really smart category with an IQ of 157. That has a frequency of about 10 in a million. I’ve met one other person in that range. He’s even smarter than I am, with a 1600 on his SATs which translates to a 160+ IQ.
In practice that translates to about a 3x clock speed in my brain. As when you overclock your computer, you reach a point where you get glitches and artifacting. This happens in my amygdala leading to treatment resistant depression. I have to get my brain hard rebooted once a month with electroconvulsive therapy (ECT). I lose some recent memories like tv shows I’ve watched. I’d gladly trade a bunch of IQ points for feeling better consistently. I’m basically Marvin from HHGTTG.