"Good breeding," Mark Twain once observed, "consists in concealing how much we think of ourselves and how little we think of others."

Not much has changed in our looking-out-for-No. 1 world since the Hannibal, Mo., humorist's day. In fact, downright boorishness may even be on the upswing.

There are even whole cities that are hotbeds of obnoxiousness, says writer George Plimpton. "New York is the rudeness capital of the world." With the possible exception of Las Vegas -- which other social observers consider too obnoxious to be considered part of Western civilization.

You don't even have to leave home to be insulted, shoved or put-upon. You just have to live in the right bad-mannered decade. The 1960s was one of them, says one etiquette expert. It was responsible for the notion that just about anything goes.

Anything or everything doesn't, but your behavior might be telling the world you think it does. And that means you're probably long on enemies and short on friends, says stress specialist Richard R. Abidin. "Rudeness is sometimes a symptom of deeper problems that are not being tackled. People with a lot of anger often go into a rage, not realizing that something else is the source of that irritation."

Are you barging through life with a big can't-get-no-satisfaction chip on your shoulder? It doesn't take long to find out. Here's a quiz that reveals whether you're Don Rickles rude or Dinah Shore polite:

1. You're inside a ready-to-close elevator. A harried figure is rushing toward you, so you:

a) push the "door close" button

b) shrug as the doors slam in the come-lately's face

c) chuckle as the doors shut

d) none of the above

2. Approaching a traffic light that just turned red, you:

a) stop and wait

b) step on the gas and speed through

c) stop but honk your horn loudly

d) give the guy who sneaked past the light ahead of you the finger

3. When an elderly person, holding four large shopping bags, stops in front of your bus seat, you

a) stay seated; after all, you got the seat first

b) nod hello but go on reading your paper

c) get up and give him (or her) your seat regardless of how tired you are

4. How often do you clean up when your dog has done "his business" on someone's lawn, driveway, etc.?

a) always

b) only when someone's looking

c) never, there are too many rules and regulations these days anyway.

5. You've had a tough day. Two not-too-smart-looking strangers from out of town ask you for directions. Would you ever deliberately give them the kind guaranteed to take them even farther from where they're headed -- just for the heck of it? Yes or no.

6. Your standard movie/theater/playhouse behavior includes:

a) chewing bubble gum or smoking and leaving the wrappings and remains wherever they fall

b) commenting aloud on the plot and characters to your companion

c) singing, foot-tapping and repetition of any good punch lines

d) none of the above

7. Which are you most likely to say when you're stopped for a traffic violation?

a) "Is there anything wrong, officer?"

b) "Give me a break, why don't you go after the real criminal?"

c) "Trying to make your quota for the day, officer?"

8. Which of the following late-night activities do you consider out-of-line in regard to your neighbor's peace and quiet?

a) break dancing

b) weight lifting

c) stripping the floor with a power sander

d) all of the above

9. Which of the following statements are you likely to make to a cab driver?

a) "I have to pay you to leave me a mile from the curb?"

b) "Where did you learn to drive like that? In (choices include Guatemala, Egypt, Pakistan or Yonkers; consult driver's ID card)?"

c) "Thanks for getting me here on time. You've got a tough job."

10. Leaving a store, you bump into a stranger and he (she) drops an armful of packages. What do you say?

a) "I beg your pardon, let me help you."

b) "Why don't you look where you're going?"

c) "Sorry, but I'm in a hurry. You'll have to pick 'em up yourself."

11. Your best friend has gotten a promotion and met a great guy (girl). Your response?

a) You're genuinely thrilled and say so

b) You say you're thrilled but you're so jealous you could spit nails

c) You congratulate her (him), but you add, "Why you? Just lucky, I guess."

12. Pushing a fellow passenger is sometimes necessary to get into a packed subway car (bus, train, elevator); otherwise you'd have to wait for the next car. Yes or no?

Answers: Give yourself one point for each correct answer: 1-D; 2-A; 3-C; 4-A; 5-No; 6-D; 7-A; 8-D; 9-C; 10-A; 11-A; 12-No.

Scoring: 12: You're practically a saint. 11-9: You're rude but not 100 percent of the time. Work on it. Less than 8: You are a walking cliche' of a boor. Get that rudeness in check. So, Shape Up

If you see yourself as a prime candidate for personality reform, here are some suggestions:

Are you obnoxious because you're undernourished? Get a nutritionist and get into a people-loving mood. The Consulting Nutritionists in Private Practice (an affiliate of the American Dietetic Association) has a list of qualified registered dietitians in private practice in all 50 states. Write: Aviva E. Croll, P.O. Box 41, Bloomingdale, Ill. 60108. Send a business-size, self-addressed, stamped envelope.

Boors are often low in self-esteem, says the director of New York's Institute of Socio-Therapy. A good once-a-day run is the best medicine.

Beat boorishness with a book. Two good ones: How to Cope When You Can't, by Don Gossett (Huntington House Books, 1986), and How to Win Friends and Influence People, the classic on getting along by Dale Carnegie, at every bookstore and library.

Can't reform? Celebrate Sourest Day ("a day for sour people") Oct. 25. Write Richard Ankli, 639 Fifth St., Ann Arbor, Mich. 48103 for details.