Like other things that we can't explain, we tend to find a way to explain it, like calling extremely good-natured people saints and extremely bad-natured people evil or demonic. IMO, it's all chemicals, and with so much variability that it is, indeed, impossible to map out every psychological manifestation and predictor.
There are SO many things that mankind does NOT understand, and might not for a very long time.
There is documented evidence that when a person dies they lose a very tiny percentage of body weight a fraction of an ounce, and that DOES not include the human fecal matter, urine, and even human flatulence when they pass. I will try and find the scientific article. So what is that small amount of weight that cannot be quantified to our eyes?
I would say that some things that look human are missing their
scientific "soul". But what are these things even though they APPEAR to look and even act human? Who knows.