The Black Cat may very well be seen as a study in human psychology because the main character is clearly a psychopath. At first you can see how the man is kind, always given to service to others, a good family man, and he is especially loving to his black cat, Pluto.
The moment when he begins to change his attitude it seems as if all the goodness that he had in the beginning of the story had been all part of his psychopath behavior, since he did a complete turn and placed all his anger towards the cat until he killed him.
Then came the psychosis and paranoia of him thinking that the cat was chasing him, until the man, himself died under mysterious circumstances which suggest that the cat did get back at him after all.
However, it is the slow decay of his kindness, and his turn for the worst what makes one wonder about his actual mental state and makes one suppose that he was indeed totally psycho.