Hasn't always been after the fact, either.
I've often made predictions of 1-2 year olds and noted that when those children got to be teens in that home, that there would be hell to pay. I was rarely wrong.
If you don't mind, would you elaborate on what you saw in those toddlers that caused you to make those predictions?
That reminds me of something a vet once told me.
He said he could look around his waiting room and tell which cats had been taken from their mother prior to 6 weeks. They were the unruly ones.