I and many of my friends are nobodies. You don’t bust their butt with a paddle, but discipline can start as soon as you recognize a child can make decisions.
The sooner a child learns there are repercussions for decisions, the sooner they learn to think.
An easy example is a mom holding a cookie, and trying to get the child to say “cookie” before she gives her baby the cookie. Of course she doesn’t wait until the child speaks with clear diction, but will wait until her baby makes an effort. Sometimes, you can see the baby trying to understand.
Obviously they can’t make decisions if they still poop in their pants.