HACKENSACK, N.J. — In study after study, as many as 8 out of 10 adults in America say spanking is an appropriate form of discipline.

What the studies don’t show is how people define spanking and where they believe corporal punishment of children crosses a line to abuse.

While those questions have long been quietly debated, the indictment of NFL star Adrian Peterson has raised them in a very public way, even if many of those who believe in spanking find Peterson’s alleged behavior abhorrent.

The story is well-known by now — the Minnesota Vikings running back has been indicted on child abuse charges for stuffing leaves in the mouth of his 4-year-old son and beating him with a switch — a tree branch — that left the boy with cuts and bruises all over his body.

The incident started a conversation among opponents and defenders of corporal punishment of children by their caregivers. The issue is so uncomfortable that pediatricians, who are supposed to ask parents how they discipline and if they spank their children, rarely broach the topic.

The question hardly comes up in discussions between parents and doctors, said Dr. Howard Mazin, an attending pediatrician at Englewood Hospital and Medical Center, because of the belief it has “fallen out of favor and people don’t do it.”

Studies, however, show otherwise. People are spanking their children and many pediatricians aren’t talking to them about it.

In a Harris Interactive poll from September 2013, 81 percent of Americans said spanking is sometimes appropriate. The number was down from 87 percent in 1995, but the position maintains a strong majority in this country and stretches across racial, economic, ethnic and geographical lines. Among parents, 67 percent reported spanking their children.

To the American Academy of Pediatrics (AAP) and experts who study physical punishment of children and its effects, there is no debate on the issue.

“The AAP does not advocate spanking and wants to discourage spanking as a means of discipline,” said pediatrician Ben Siegel, immediate past chairman of the academy’s committee on Psychosocial Aspects of Child & Family Health. “The AAP wants to discourage spanking and corporal punishment because the AAP recognizes that spanking can be severe and lead to child abuse.”

Corporal punishment is a health and safety issue for children that persists because of embedded cultural beliefs and indignant parents not wanting to be told how to raise their children, according to experts.

Studies have consistently shown children who receive any kind of corporal punishment are more likely to be more aggressive and defiant in the future and at risk for mental health issues. Despite this research, Americans are unswayed.

While nearly 40 countries have laws against the corporal punishment of children, the United States not only does not outlaw it, but many Americans continue to embrace it as the proper way to parent.

“Part of our social norms are physical punishment,” said Siegel, who is also a professor of pediatrics and psychology at Boston University School of Medicine. “This is embedded in our culture.”

The academy’s policy statement says: “Spanking has negative consequences and is no more effective than other forms of discipline. In fact, there’s often a gray area between when spanking ends and child abuse begins.”

Unlike healthy eating, car seats and wearing bicycle helmets or sunscreen, the elimination of corporal punishment is not part of public health and education campaigns.

“The national organization has that statement, but it hasn’t trickled down to everyday interactions with pediatricians,” said Elizabeth Gershoff, one of the leading experts on parental discipline methods and corporal punishment of children.

The pediatric academy’s policy statement was written in 1989 and stands today, but even those within the organization acknowledge an issue with semantics.

“It depends what you mean by spanking and it becomes somewhat complicated,” said Siegel.

Laws often define child abuse as “the infliction of excessive corporal punishment” but what is excessive? Where people place that line seems arbitrary at best. Is it using an object other than a hand? Causing welts or bruises or bleeding? Is it the age of the child or the behavior that sparked the spanking? When does spanking become abuse and is either OK?

“There’s a difference between spanking and child abuse but that doesn’t mean either are correct,” said Mazin.

Studies show corporal punishment doesn’t work to bring about better behavior long term.

“The research couldn’t be any clearer,” said Gershoff, an associate professor of human development and family sciences at University of Texas at Austin.

Sometimes it isn’t even effective in the short term. A pilot study published in June in the Journal of Family Psychology showed that 73 percent of children would misbehave again within 10 minutes of being spanked. It was a small sample, but had revealing results.

“That answers the question of the immediate impact of the spanking,” Siegel said.

People don’t want to hear the message, though, Gershoff said.

“They don’t want to be told by people like me from the academic ivory tower,” she said. “They firmly believe it’s working when there’s no real evidence it’s working.”

Many will argue spanking does work, citing anecdotal evidence and reminiscing about days gone by when children were more respectful. They draw a direct line between more frequent physical punishment and children toeing that line.

“We live in a society now with our kids in the African-American community — and I’m only speaking on that because I live in it and I’m part of it — I’ve seen parents who use the non-corporal process, a lot of those kids are not (well-behaved) the way the kids were years ago,” said Della Fischer, an associate minister at Calvary Baptist Church in Paterson.

Parents are caught in an unwinnable situation when it comes to physical punishment, she said.

“You don’t (hit) your child, then your child becomes a menace to society, then someone says that your child wasn’t raised properly,” Fischer said. “You spank your child to show some form of discipline, then they say you abuse your child. It’s like you’re danged if you do, danged if you don’t. And it’s such a fine line.”

Fischer draws her line at leaving marks or injuring the child and parents “losing control.”

In the Peterson case, while many were appalled by the photos and charges, others have stood up to defend his right to discipline his child or cite the African-American culture or their own experiences growing up whatever their ethnicity as a way to explain the behavior.

“I’m from the South,” former NBA star Charles Barkley said in a television interview. “Whipping — we do that all the time. Every black parent in the South is going to be in jail under those circumstances.”