I remember studying this in my high school Sociology class. The experiment of the wire-mesh mothers, in which some baby monkeys, deprived of their real mothers, were given fake ones. Some of the fake ones were furry and warm and some were just made of wire mesh. The monkeys that got the wire mesh grew up to be screwed up adult monkeys. We know that human babies, if likewise deprived of human contact, being held, for example, end up much the same way. There were a bunch of orphans from Romania (the homeland of the vampire, which is why I’m writing about this here on this site) that were provided with food, shelter, medical care, all that they needed—except human contact. And not a few of those thus-deprived babies, having been adopted by families in America, grew into adults with serious issues.
It is believed by psychologists and psychiatrists that deprivation of this sort must take place within the formative period, the first year or so of life, to create a psychopath/sociopath. I don’t mean to suggest that all those orphans ended up that way. But some sure did. This linked article revisits that infamous case and catches up with one of those babies, now an adult. It’s fascinating stuff, if you’re into psychology, or even if you’re not.