So the more practically-inclined may be asking: is there a reason to bother with Pokémon-Amie if you’re not into the virtual pet aspect? Well, as your Pokémon’s affection rating goes up, a variety of things can happen in battle - sometimes very beneficial things, as it were!
Generally, if you see a heart or your Pokémon looks at you during battle, then, yeah, it was caused by Pokémon-Amie. Note that the following effects do not occur in online competition, just the single-player experience.
- Additional battle messages to evoke emotional reactions from you. (i.e. "It looks like it's about to cry" may appear at low HP.
- You may pet the Pokémon after a battle as if you were rubbing the Touch Screen.
- Your Pokémon's critical-hit ratio can be increased.
- Your Pokémon's evasion rate can be increased.
- Your Pokémon may recover early from status ailments, even normally permanent ones like Poison or Paralysis! (KO will not, however, be healed early. It's in-battle only.)
- The EXP. earned by your Pokémon is boosted by 20% when it has an affection rating of 3 hearts!
- Your Pokémon may survive attacks that would KO it!
Furthermore, one of the requirements to evolve Eevee into the Fairy-type Sylveon is to obtain an affection rating of 2 hearts (in addition to having a Fairy-type move such as Charm).