DALLAS - "No, sir." "Yes, ma'am."

Catherine Lundberg likes hearing those conversational niceties.

"Any time you esteem others, it's a good thing to do," she said.

But while her boys, ages 8, 12 and 14, are in the habit of using the courtesies, they occasionally need a reminder.

Connie Bearden of Frisco, Texas, says she used to respond with a sassy "I'm not your servant" when her mother would ask her to use sir and ma'am. But today, she teaches her own 3-year-old daughter to use those very words.

Etiquette experts say those once necessary Southern niceties are falling from favor in schools, at home and on the job. They blame society's overall decline in manners and a steady drop in the use of formalities.

Lynda White, who was taught by her parents to use sir and ma'am, acknowledges that social exchanges are becoming more casual.

"There is a decline, but any time you use it, you can't go wrong," said White, who operates Dallas-based Texas Etiquette, a business that teaches correct social behavior to youths and business professionals.

"Even if I'm in New York City and I say, 'Yes, ma'am,' they say, 'You must be from the South.' It shows a certain level of respect when you use sir or ma'am."

Ron Butters, professor of English and cultural anthropology at Duke University, said it would be a mistake to assume that the use of sir and ma'am is exclusively a Southern phenomenon. He said students from around the country have addressed him as sir in his 35 years of teaching, and that it denotes the power relations between speaker and hearer.

But Cindy Post Senning of the Emily Post Institute says the terms are clearly "quite regional."

"I'm up in New England, and it would be very unusual to hear sir and ma'am," Senning said. "In areas of the South, it's a very polite and mannerly thing to do. The important thing to do is to know the culture of your region."

The use of sir and ma'am flourished in the South more than any other region, says Guy Bailey, a linguistics expert at the University of Texas at San Antonio, who grew up in Alabama.

"It's absolutely more prevalent in the South, no question. People in the South have always valued courtesy and polite behavior," he said.

He doesn't know if sir and ma'am usage was tied to the stratification of society during the slavery period, but adds "the Southern notions of courtesy were formed during that era." He blames the migration of Northerners during the 1970s for the downfall of the honorifics.

Elaine Gathy, director of the posh Creme de la Creme preschool in Colleyville, Texas, said children learn to use Mr. and Mrs., but not sir and ma'am.

"This generation of parenting, you just don't hear it," she said. "It's taboo and has kind of died out."

Not that Gathy would mind teaching it again.

"I'm sorry to see it disappear," she said. "I would love for it to be popular again."

Charlene Levering, a retired Dallas etiquette teacher, remembers when sir and ma'am were commonplace. Now, she said, they're so seldom used that they almost sound out of place.

"In my generation, it was so obvious if you didn't give a title to a person," she said. "It was as if a person didn't finish a sentence."

Not everyone is wistful about the words' loss of popularity.

Grant Barrett, a project editor for the Historical Dictionary of American Slang, says he welcomes the change.

"There's not that level of intimidation. There is something about the respect that goes with the title, whether it's deserved or not."

Although the courtesies may be fading from public discourse, they're still widely used in military and law enforcement training.

At the Arlington, Texas, Police Department Training Academy, recruits must use the terms in all manners of address. Then they generally continue the practice once they graduate, Sgt. Craig Leondike said.

The courtesies are widely used but not required in speaking to civilians.

"We have directives to behave in a courteous manner," Leondike said. "It doesn't dictate to use sir or ma'am, but they leave with the common knowledge that's a preferred term when dealing with the public."

The Junior Cadet Corps in Fort Worth, Texas, teaches seventh- and eighth-graders that such courtesies are important in addressing superiors.

"If they forget, we drop them for push-ups or have them write an essay," Chief Warrant Officer Jeremiah Marshall said. "After three or four months, the kids buy into it and then it becomes fun. It's just showing respect."