Ok, so I was checking through my PC Box, and I saw a Pokemon with the Serious nature. I checked to see what it did, and no stats goes up or down. I know of 1 useless nature in Serious. How many more are there? Why are there natures with no effect?
I think that this is just a free nature, so that everything is even. It can also be because to keep the natures balanced.
Hope this helps!
>Every Nature represents one of the 25 unique possible combinations of stat increase and decrease; thus, there are five Natures that have no effect on the Pokémon's stat growth (Bashful, Docile, Hardy, Quirky and Serious). These five "neutral" Natures are technically Natures that increase and decrease the same stat.