When I was young I was sadistic in the way described by OP. Up until about age 7 I did not too nice things to my pets and younger sister, pets just to hurt them, sister that just because mixed with jealousy from no longer being an only child attention whore. They're not pleasant memories. *random self-reflection* For whatever reason it seems as though I had no concept of the pain of others, like they were somehow inanimate and lacked the agency required to cause pain in return.... Come to think of it, I only held any level of respect for people who hurt me. Yet apparently these same others didn't anticipate any change in me, because they kept doing it.
Moral development seemed to skyrocket by 8 though. I mostly credit grandparents and teachers.
