> I think the articles talks about this: the child still wakes up in the middle of night but does not cry
The child is avoiding crying in the absence of its parents because doing so would cause predators to find him before his parents. Evolutionary instinct. The parents will (hopefully) return from hunting & gathering eventually, to pick the child up.
And when the parents regularly fail to return or never return - yeah, one way ticket to a psychological disorder.
Only with sleep training, the parents do return in the morning, so what's your point?
Of course a neglected child is likely to grow up with a psychological disorder. Neglected as in the parents (or at least some carer) not being there for days on end, or simply abandoning them. That's not sleep training though.
The child is avoiding crying in the absence of its parents because doing so would cause predators to find him before his parents. Evolutionary instinct. The parents will (hopefully) return from hunting & gathering eventually, to pick the child up.
And when the parents regularly fail to return or never return - yeah, one way ticket to a psychological disorder.