I used to talk to my baby like he knew what I was saying. EX: Isaac i ased you not to pull my hair, please let go. Thank you! (baby's 2months)
People would ask me why do I talk to him that way, he can't understand. I would say I know, but when will I get a letter in the mail telling me when he will?
What I think is say it in words they understand but don't assume they wont. My son is 4 and has always been very empathetic. But I also always expected him to be. Im not saying he wouldn't hurt animals or be mean to others but I always made him say sorry and have consequences for what he did. If he hurt the cat he couldn't touch him any more for a while (time limit per age) if the cat scratched him then I would say ya it hurts. Kittys mad at you because you were mean. I would still kiss it but I let him understand why kitty did it.
Somtimes teaching empathy means letting them hurt too. My son was breaking puzzles at the daycare and wouldn't stop. After two week of this I realised that talking wasn't working. I got an old puzzle of his sat in front of him and broke it. He was flaber-gasted
Son: "Mommy, why would you break my puzzle?"
Me: "because i wanted to see if it would."
Son: "Oh, Thats what I said to the daycare. Well don't break any more."
I broke another, he cried
Son: "Mommy, I asked you not to break any more!"
Me: "well didn't we ask you to stop breaking the daycares puzzles?"
Son: "ya."
Me: "And did you?"
Son: "No. I wont do it any more. I will tell them sorry tomorrow."
Me: We need to replace the ones you broke with one of yours."
Son: "I know! We can give them my dinosaur puzzle!"
Talk to them about their feelings and other peoples feelings. let them see you cry if they hurt your feelings, they love you so much it works fast. They are so smart. There is never a too early to start.
Sorry it's so long. I find stories are the best way to explain.
good luck