Last night, my sister and I were up late in my room with the light out, chatting about all sorts of random things. Suddenly, there was an eerie silence, and then we heard a scratching noise that sounded like someone's nails scraping our walls. My sister got freaked out and turned on the light, and we looked around, thinking that it had been made by my cat. My cat was locked in his cat carrier for the night, so it couldn't have been him. After a while, I managed to calm my sister down by talking to her a bit. The whole ordeal didn't really bug me, mainly because I'm a paranoid schizophrenic and I see and hear things that aren't there most all the time, so odd sounds are no stranger to me.

Well, we went back to discussing things, and it wasn't but about five minutes after the first round of scratches, before it happened again, this time louder and longer than before. My sister once again leaped up and turned on the light, and she was severely scared. She didn't even want to be down in my room anymore. At this point, I was a little bit freaked out, but trying not to show it. We looked around to see if anything could have made the noise, but there was nothing capable of making that sort of noise. For the record, my bedroom is located in the basement of the house, and is almost always freezing. We called my mom down, and she sat and talked with us for a little while. We turned out the lights to see if it would come back, but it didn't.

Eventually, I got severely annoyed with everyone congregating in my bedroom, so I yelled at them a bit, and they left to get some tea. I was alone in my bedroom, and I hear breathing and footsteps coming from just outside the door, and the springs on the cot in the corner of the bedroom were creaking. I heard soft mumbling later on, but no one else could, so I attributed all this to my psychosis. Nothing else happened for the rest of the night, and I managed to get a halfway decent sleep.

Any thoughts on what this could have been? I'm thinking it might have been rodents, but we don't live in an area that seems to have many of them.

A rat, a cat, a racoon or another mammal perhaps. Maybe that would explain why it stopped scratching when you turned on the light. It doesn't nescesarily have to be something paranormal, thinking that would just freak you out even more. It could've been a whole lot things.

Hello Arcanum, and welcome to the forum.

Well since you weren't alone and have someone else who heard the noise too, then you know it wasn't just your imagination.
I think that your first guess is most likely the most logical one, rodents. Even though the home may not seem to be the type that would get rodents it may have. Squirrels and other things could also account for the noise/sound of scratches.

Look around for evidence of rodents, around the attic or other areas that you can look (vents around a dryer vent, that type of thing). Is it a half basement or full? If half there may be enough of a crawlspace for pests to enter.
I really applaud you for the fact that you are looking for logical explanations first!

Regards,
Mabon.