Do natures have any effect on EVs?

Question

Okay, before you write this off as the stupidest possible question on the planet, hear me out. In a playthrough that I'm doing, I have a Gardevoir. It has a brave nature, since I was tired of looking for Ralts that seemed to refuse to show up by the time I found one with Synchronize. Now, before the league, I decided just to go all out and hardcore EV train my Gardevoir. I went to Oreburgh Gate and murdered every Zubat and Psyduck in sight with a held Macho Brace. I fought about an equal amount of Zubats and Psyducks, and I gained +3 in speed. However, I also gain +17 in special attack. I was a little confused, so I just fought another level's worth of exclusively Zubats. I got +2 in speed from that level up. And now here I am, looking through Bulbapedia articles and finding nothing about EVs and natures and base stats and all that. Does anyone here have any idea what's going on? (I'm playing Platinum, for anyone wondering)

Comments

When are you measuring how many evs you have?

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It's possible that you already have max speed, or the +17 was because of Gardevoir's base special attack in addition to EVs. Also Psyduck is more common than Zubat when you're surfing.

Answer 1

Natures do not affect EVs, they definitely affect stats but not EVs. To answer how you may have gotten +17 in SpA, whilst you got +3 in Speed, it could be the fact that you may have miscounted how many you killed OR maybe you miscounted how much SpA you had before the EV training.

Answer 2

Natures can either lower or raise the specified stats, for example a brave nature ups Attack but lowers Speed. Since you killed an equal amount of psyducks (special attack raised) and zubats (speed). As sumwan mentioned in the comments you probaly have max speed or Gardevoir's base special attack in addition to EVs.

Edit: You have a brave nature, it lowers speed.