Psycho, don't undertsand.?

I'm not quite sure what the person is saying about "not quite right with today's science" as it's been said that the movie gives a realistic view of psychosis. Thank goodness for an interesting cl on serial killers at my college to help me with that. But no, his mother persona has just been created by his mind. It would be like you were psychotic and took on a personality in which Abe Lincoln wants you to murder Peter Pan. The real Lincoln wouldn't have done it, but you've lost perception of reality so it blurs the lines of what's real and what's not.