Pokémon Gold and Silver

Nine-and-a-half: this is the sort of mental age I ascribe to Pokémon. To first playing it, that is, but you could say it probably also fits the mental age of Pokémon themselves, too, in a roundabout way. It's that weird bit of life you occupy right between having an adult brain and a child's - right after you start to pick up a moral compass that goes beyond just doing what you're told, to a sense of duty or justice, but right before you're really sentient enough to start thinking about why that is. Permit me to really overcommit to a point here: as humans, we are probably closest to Pokémon when we're about nine-and-a-half.