> Since there are meaningful zeroes for speed or flexibility or throw distance, it must also be meaningful to discuss doubling the effect of fitness on them. I

> Since there are meaningful zeroes for speed or flexibility or throw distance, it must also be meaningful to discuss doubling the effect of fitness on them. If the effect of fitness on speed is small (as a fraction of absolute speed), then doubling the effect has little to do with doubling speed. If it's large (order unity), then we don't generically expect to be able to double the effect while staying in the regime where intelligence is well defined. These two notions of double are just completely different -- one is a derivative, one is a magnitude -- and it's a mistake to link them.