Have you ever witnessed someone do something horrible and wondered if you’re just as horrible as they are? We all have—some of us more than others.

After 18 years of research, I have carefully comprised the 15 ultimate signs that characterize a horrible person. Studies have shown (read: I have decided) that if you catch any of these symptoms early on, you can actually become, well, a better person.

For the sake of humanity, future roommates, and future generations, read on to find out if you possess any of the terrible characteristics which might make you a bad person.

1. You chew loudly.

If the volume of your chewing is louder than the volume of the person who is trying to have a conversation with you, you need to work on something. There’s really no biological reason for this, so something must budge.

2. You have horrible grammar.

If you can’t figure out when to use “you and I” versus “you and me,” we can’t talk. Further, you cannot do “good” on a test (unless you’re doing some act of kindness on your test), you can only do “well” on a test. Please get these straight.

3. You don’t smile at people you know as they walk by.

If I know you and I see you on campus and you don’t acknowledge my existence, I will unfollow you on all of my social media platforms. Sorry, not sorry.

4. You don’t hold the door open for the person behind you.

I don’t care if you’re of the female gender or the male gender or anything in between. If you see someone walking into a lecture hall directly behind you, you hold the door open for them.

5. You only talk about yourself.

Believe me, no matter how wonderful you may think you are, chances are people don’t want to center all of their conversations with you around you. Ask your friend how they're doing for a change; this could be life-changing.

6. You frequently interrupt people while they’re speaking.

This one speaks for itself. Don’t interrupt people to tell your story (as awesome as you think it might be).

7. You boast about yourself and your accomplishments.

I’m sure that you’re doing wonderfully in your aqua-aerobics class, and that your teacher told you that you may have a serious future in the aqua-aerobics industry, but nobody wants to hear you drone on and on about how wonderful you are.

8. You frequently show up late to events.

Unless you are the Queen of England, you have no excuse to show up late. If you know that it might take several hours to get ready, start doing your makeup (read: painting your face) earlier.

9. You don’t let people merge into your lane while driving.

Would it really kill you to let me merge into your lane on the freeway? Never in the history of driving has anyone ever not arrived at their destination because they let a person merge into their lane on the freeway.

10. You watch people nearly face death on the bike path and don’t offer them assistance.

If you witness a skateboard versus bike collision and you’re not immediately there to provide moral support, you’re a terrible person. (Side note: If the collision is very minor, it is always best to pretend you never saw it happen so as not to embarrass the klutz involved).

11. You regularly tell people that you should do lunch with them but never follow through.

We all know those people who frequently shout “we should do lunch” after an interaction with an acquaintance. What we also know is that these people never actually acquire said lunch with their acquaintances. Just drop the line.

12. You post pictures on Facebook without regard to how others may look in them.

As long as you look great in the photos, you post them. Don’t do this.

13. You borrow your friend’s clothes (with or without asking) and return them in a different condition than they were when you first snagged them.

If you borrow clothes that do not belong to you, you better treat them like you would your future child. This means no stains and no rips.

14. You’re rude to people who are serving you.

If you’re condescending to a waiter or waitress, I will not go out to dinner with you, ever.

15. You walk slowly in front of people who are trying to get places.

Not everyone has the luxury of traveling out of a lecture hall at zero miles per hour. Hurry up or move out of the way.