Simple is an ability used in the Pokémon video game series. Currently, only five different Pokémon use it. The ability doubles the potency of stat raising and lowering moves. It was introduced during the Sinnoh region.
Changes between games
In Generation V, it was changed so that all stat changing moves' effects just were doubled instead of the stat boosts themselves. The stat boosts altogether cap out at 6 stages like with other Pokémon instead of being capped at 3. Moves like Psych Up or Baton Pass properly transfer stages (i.e. the full six stages instead of 3 stages). The flavor text is also fixed to say the stats "rose sharply" instead of just" rose".
The move Simple Beam changes the ability of the Pokémon to Simple.