So the study shows fathers tend to neglect children from his first wife after he marries a second wife.
In addition to, under conservative orthodox interpretations of Islamic law, all children belong to him. He gets custody. Doesn't matter if his kids are from sex slaves or four wives, these children legally belong to him. Does it make sense for a child not to know his/her mother? Anyways this is a little sidetracked but you get the point about polygamy. See the following posts I did about polygamy and how it is no longer usable in Islam: