You could always ask. Even if they can't talk, all the Pokémon I've seen are pretty expressive.

[Granted, animal body language can be tricky to read sometimes, but after six years, it's not quite as jarring.]

But honestly, I'm more concerned about the Pokémon like Yamask and Phantump. I mean, they used to be humans, and now they get captured like any other Pokémon.