In "The Black Cat" by Edgar Allan Poe, how do the narrator's feelings differ when he kills the cat and when he kills his wife?

The
narrator in "" is an obvious sociopath, incapable of feeling true remorse or guilt.
Nevertheless, as he tells his tale, he recounts a regression into further depths of depravity.
Therefore, when he kills his first cat, Pluto, he is somewhat horrified at his deed, and for
months it bothers him with a "half-sentiment that seemed, but was not, remorse."
Still, as he reports it, he is not satisfied with himself after killing the cat, and he plunges
further into alcoholism.

After killing his wife, however, no such
half-sentiments plague him. Instead, he is intent on covering up his crime, and when he has
carefully hidden the corpse behind a...