WHEN Murray Straus was raising his children in the 1950s and '60s, spanking was de rigueur in the American household. The Straus residence was no exception, with the father of two occasionally reacting to their misbehavior with a swat to the bottom.

But times have changed, and so has Straus' perception of spanking.

"If I knew then what I know now, I would not have spanked them at all," he says. "My research has convinced me that there should be no hitting — never, under any circumstances."

Straus, co-director of the Family Research Laboratory at the University of New Hampshire, has long advocated doing away with spanking. And many psychologists and pediatricians also now say that parents should never strike a child. Assemblywoman Sally Lieber (D-Mountain View) has even promised to introduce a bill in the California Legislature that would make it illegal to hit those younger than 4.

Frequent and impulsive spanking is clearly detrimental, researchers agree. Other kinds of physical punishment, including hitting children with objects, are harmful as well. "Corporal punishment has really serious side effects," says Alan Kazdin, a professor of psychology at Yale University and president-elect of the American Psychological Assn. "Children who are hit become more aggressive."

Yet the mildest forms of spanking have not been proved harmful. "A family that hits once in a while? The research is equivocal about that," Kazdin says.

What the research does show is that spanking is generally no more effective than nonphysical disciplinary techniques in instilling acceptable behavior, that its effects vary from culture to culture and that a greater frequency of spanking increases the risk of negative consequences.

Although some researchers say it can play an occasional role in supporting more lenient forms of discipline, Kazdin argues that spanking should be avoided even if it is harmless.

"It suppresses [misbehavior] momentarily. But you haven't really changed its probability of occurring," Kazdin says. "Physical punishment is not needed to change behavior. It's just not needed."

Reasons not to spank

Spanking can escalate toward physical abuse, potentially injuring the child, and can contribute to later emotional and behavioral problems, according to the American Academy of Pediatrics. It's also less effective than alternative disciplinary tactics, and it's a hard habit to break, the organization says. Studies have shown that people who were spanked as kids tend to spank as parents, perpetuating the cycle.

During the last decade, a raft of studies showed that kids who get spanked are more likely than their peers to display behavioral and emotional problems later in life. The more frequently they're spanked, the more harmful the consequences tend to be.

In a 1997 study in the Archives of Pediatric and Adolescent Medicine, for example, Straus and two colleagues found that 6- to 9-year-olds whose mothers spanked them at least weekly were more likely, two years later, to behave antisocially than were kids whose moms didn't spank.

The researchers interviewed more than 800 mothers and asked how often their kids did antisocial things such as cheat, lie, bully, deliberately break objects or act disobediently at school. Taking into account the degree of antisocial behavior that each mother said her child displayed at the beginning of the study, Straus' team concluded that spanking probably contributed to increases in bad behavior seen during the study.

Nevertheless, Straus notes, a "lucky majority" of kids who get spanked suffer no discernible harm.

Another 1997 study also linked spanking to subsequent antisocial behavior, and it additionally found that children who were spanked at the beginning of the five-year study were more likely to be getting into fights at school by the end of the study. (An exception was African American kids, who were less likely to fight if they'd been spanked than if they hadn't. More on that in a bit.)

Since then, other studies that have tracked kids over time have linked corporal punishment to higher rates of children later assaulting their parents and higher rates of boys assaulting their girlfriends years after they themselves were smacked.

Spanking "gives the message that force is a justifiable method of solving conflicts," says Daphne Bugental, a psychologist at UC Santa Barbara. "The child is learning a lesson: If you run into a conflict, use power, use force."

Adds Shari Barkin, a pediatrician at the Children's Hospital at Vanderbilt in Nashville: "It teaches children that when you're angry, you should hit people." Spanking also appears to have a detrimental effect on the brain. In 1999, Straus found after a two-year study that 2- to 9-year-olds who were spanked developed less rapidly, judging from cognitive tests, than other children.

In a 2003 study, Bugental and her colleagues delved deeper, examining the effect of corporal punishment on brain chemistry in infants younger than 1.

Those who were spanked frequently, they found, showed exaggerated spikes in the stress hormone cortisol when they were subjected to a novel situation, such as being in the presence of a stranger after their mother had left the room.

"They were very easily frightened," Bugental says. "They tend to be more afraid of things generally."

By contrast, she says, "in the children who had not been spanked, there was hardly a blip" in cortisol. Researchers haven't yet determined whether spanking has similar hormonal effects on older kids.

Cortisol imbalances could potentially lead to impaired coping abilities, social and emotional problems and cognitive deficits, Bugental says.

In support of spanking

Spanking has its supporters, of course. A couple of swats to a child's behind has a well-deserved place in discipline when milder tactics fail, says Robert Larzelere, an Oklahoma State University psychologist who has been researching corporal punishment for more than a quarter of a century. Larzelere describes that circumscribed use of corporal punishment as "conditional spanking."

"It's better, wherever possible, to offer verbal correction and explanation," he says. "But then back that up, first with nonphysical consequences, and then, if the child acts defiantly, with conditional spanking."

For example, he says, if a child refuses to sit in a chair during a timeout, then a light spanking would emphasize the need to cooperate with that form of discipline.

"If it's used as a backup for the timeout, then the next time, the child is more likely to cooperate with the timeout procedure," Larzelere says. Parents "can then phase out the spanking.

"I think it's a minority of spanking that fits this conditional definition," he adds. "For [all] the usual ways that parents use spanking — combining the good, the bad and the ugly — its outcomes are neither better nor worse than any alternative."

The effects of spanking may depend not only on how and when it's meted out but also on the cultural context.

In a study published in Child Development in 2005, researchers at Duke University interviewed 336 pairs of mothers and children in six countries in Asia, Africa and Europe about discipline and behavior. They found that physical discipline seemed to have a stronger negative effect on children in countries where it was not the norm than in countries where it was practiced widely. Several other studies, including the 1997 one that found differences between African Americans and whites, suggest that cultural differences also influence the effect of spanking in the U.S.

"Spanking may be detrimental in some families but not in others," says Eric Slade, a social scientist at the University of Maryland School of Medicine.

In 2004, he and Lawrence Wissow, a pediatric and adolescent psychiatrist at Johns Hopkins University, found that white children who were spanked before the age of 2 were twice as likely as other white kids to have behavioral problems in school.

But spanking didn't appear to lead to misbehavior in African American or Hispanic children, the researchers reported in the journal Pediatrics. "In minority cultural contexts, spanking could be more the norm and consequently less commonly perceived [by the child] as being harsh or unfair," Slade says. As long as spanking isn't perceived as unfair, he adds, "it could have a positive and constructive effect … and establish what the limits are on misbehavior."

Too often, researchers lump all kinds of spanking or even all forms of corporal punishment together, Larzelere says. Whenever an analysis links "spanking" to detrimental effects, he says, "conclusions are inappropriately made about even the mildest form of spanking."

But because researchers harbor ethical reservations about asking or even knowingly permitting parents to spank their children, few experiments have been conducted in which parents were given explicit instructions about how to use spanking to maintain discipline. "There will never be the gold-standard study," says Michael Regalado, a developmental-behavioral pediatrician at Cedars-Sinai Medical Center in Los Angeles.

And researchers disagree in their interpretations of the few such experimental studies to date, which clinical psychologist Mark Roberts and his colleagues at Idaho State University conducted during the 1980s.

In dealing with a few dozen rebellious children ages 2 to 6 — whose out-of-control behavior had driven their parents to seek professional assistance — the researchers asked some parents to spank kids who refused to stay on a timeout chair and taught others to briefly confine noncompliant children to their rooms.

In several such experiments, each approach worked about as well as the other, and both worked better than alternatives such as physically restraining the child in the chair.

Although spanking increased compliance with timeouts in those experiments, Roberts adds, it was accompanied by more crying.

"Since spanking demonstrates aggressive behavior to children, I recommend sending children to their rooms instead of spanking them," Roberts says.

Straus infers: "It didn't work any better, and it had an emotional cost."

Larzelere offers the opposite perspective. Spanking, he says, was one of the "best ways to enforce cooperation with the timeout. Even these very difficult children learned to cooperate."

Decline in popularity

Even without a law in effect, the popularity of spanking has fallen considerably in recent decades, at least among parents of school-age children.

"In 1975, we found that two-thirds of parents were hitting 13-year-olds" at least once a year, says Straus, who along with his colleagues has conducted a series of parent surveys. By 1995, that fraction had fallen to one-third. Moreover, in 1999, 52% of parents believed corporal punishment is sometimes necessary, compared with 94% in 1968.

Last month, in Clinical Pediatrics, Vanderbilt's Barkin published survey results detailing about 2,100 parents' disciplinary practices with 2- to 11-year-olds. Parents today, she found, more often reported using enforced timeouts or removing kids' privileges than they did spanking.

However, Straus says the prevalence of spanking among 2- to 4-year-olds has remained basically unchanged. As of 1995, 94% of them had been spanked at least once in their lives, according to surveyed parents. Children in that age range and younger would be covered by the proposed California ban.

But even opponents of spanking have reservations about the proposed bill. Criminalizing spanking could make it more difficult to root out corporal punishment, they say, because the threat of the law could dissuade parents from seeking help to change their disciplinary habits.

"It may drive [spanking] underground, and it definitely won't address the issues that parents need addressed to avoid spanking," Regalado says. "The bill should be framed to help parents who'd like help with their discipline practices."

Parent training programs were expanded in Sweden after that country banned corporal punishment in 1979, and in some other European countries that followed Sweden's lead. "I'd like to see legislation in California and everywhere modeled on Sweden's," Straus says.

"I'm not in favor of a law with criminal penalties," he says. The proposed California law "would do the very thing it wants parents not to do — use harsh punishment to correct misbehavior."

As for maintaining discipline among Straus' progeny, no law is needed. His past use of spanking hasn't left his grown children with any apparent psychological wounds, he says, and neither of them spanks their own children. "They are among the lucky ones who have escaped the harmful effects," he says.

"If you do it rarely, the probability of harmful side effects is low," he says. But, he contends, the possibility of harm from spanking "is never absent. Since other methods of correction and control work just as well, why put that child through even that small risk?"

Verbal attacks can be more hurtful than physical ones

Most experts warn parents against not only spanking but also yelling at or disparaging children.

Although targeted verbal reprimands may be effective in immediately halting or reducing undesirable behaviors, frequent and indiscriminate reprimands become ineffective and reinforce undesired behavior, they say. Attacking a child's character is particularly counterproductive.

Research on the subject is limited compared with that on corporal punishment, Robert Larzelere of Oklahoma State says, but verbal hostility may actually lead to more detrimental consequences for the child than does even physical abuse.

A study seven years ago on post-traumatic stress disorder found that victims tended to have childhood memories of being often put down or ridiculed. As potentially harmful influences go, such verbal attacks ranked roughly on par with memories of being pushed and shoved, although lower than a history of sex abuse.

In an earlier study of more than 3,000 parents and their children younger than 18, Murray Straus of the University of New Hampshire and his collaborators linked both verbal and physical aggression by parents to aggressive behavior, delinquency and interpersonal problems in the kids. The psychological abuse, in fact, was the more harmful of the two.

The only difference, Straus says, is that verbally attacked kids tend to lash out at others with words, while kids subjected to corporal punishment use physical hostility. Those connections applied to both boys and girls, regardless of age.

Researchers led by Michael Regalado of Cedars-Sinai Medical Center in L.A. found in a 2004 analysis of survey data that 67% of some 2,000 parents reported yelling "sometimes" or "often" at children age 19 to 35 months. An additional 24% admitted to yelling at least "rarely." Only 26% of the parents said they spanked kids sometimes or often.

"More than a third of families feel like they're ineffective with discipline tactics," says Vanderbilt pediatrician Shari Barkin. Yelling, like spanking, is often a symptom of the resulting frustration, she says. "The yellers, they're the ones who feel most ineffective. They lost control."

— Ben Harder