I occasionally wonder about this because I know a little girl who, though I don't think she could possibly be called a psycopath, does seem to demonstrate markedly different behaviour from literally every other child I have ever met (and I include the 'naughty' ones or the 'spirited' ones in this).
She is able to manipulate others, all children but also adults. Her mother, for example, is totally manipulated by her to the extent she ignores the evidence of her own eyes and ears ALL THE TIME because her daughter will tell her that X was not Y and that A was not B and that child Z was in fact the one being mean to her and not the other way around.
If there is a child crying/upset, this child is ALWAYS the one walking calmly away from the scene. She is like a homing beacom, a group of kids is just there getting along broadly OK and then this child turns up and within moments, something is said (she is careful not to say things so adults can hear) and a child is in tears.
On the rare occasion she is challenged by her mum, she ends up convincing her that the other child started it and that she did nothing.
I have heard expressions of deliberate and chilling cruelty come out of her mouth; she is the most verblly aggressive child I have ever encountered. It goes way beyond the usual silly 'you're not my friend'. It is almost always entirely gratuitous and out of the blue.
She doesn't seem to care one jot when she reduces the others to tears.
She is upset to hysterics (which can seem extremely put-on) by the smallest slight from another child. Even something that could in no way be taken as an offence can set her off and she will rage for hours.
I tend to look for the best in everyone, especially children, and am rarely disappointed. As I say, even so-called 'naughty' kids can be sweet, charming, funny, loving, just kids really.
This child sets my sense on edge and I do not trust her one jot.
Far too unqualified to say how things will turn out with her. But she's got the potential, I feel, to turn out quite nasty if she doesn't change at some point.