answer:Direct experience, by far. In terms of the amount of sheer information encoded in the brain, I’d bet that the majority of that happens by age 5, and virtually all of that is acquired experientially. It’s not knowledge in the sense of facts, but it’s the essentials of how to communicate, make sense of the world, operate a body, get along with others. That all has to be learned, and it represents an incredibly prodigious amount of information, all from experience.