More than a quarter of all U.S. teenagers think violent behavior is at least sometimes acceptable, and one in five say they behaved violently toward another person in the past year, according to a new poll.

Most said self-defense (87 percent) or helping a friend (73 percent) were acceptable justifications for violence. But 34 percent said revenge was a sufficient motivation. The poll was conducted by Opinion Research for the school-support organization Junior Achievement and the tax and consulting firm Deloitte, LLC.

More than three-fourths of the respondents who said violence is acceptable also consider themselves ethically prepared to enter the work force. That sticks in the craw of David W. Miller, director of the Princeton University Faith & Work Initiative and a professor of business ethics at Princeton University.

In an analysis released with the poll, Miller suggests the survey results bode ill for the future workforce. It's not clear that's the case, however. In fact, teens are known to think differently than adults because their brains have not matured. Scans reveal that teens' ethics change dramatically as they grow into adulthood. Or do they?

'Highly troubling'

The survey of 750 young people (half boys, half girls) age 12 to 17 was conducted between Oct. 9 and Oct. 12. The results were released this week.

"It is highly troubling that so many teenagers have a self-image of ethical readiness and the confidence in their ability to make good decisions later in life, yet at the same time freely admit to current behavior that is highly unethical," Miller said in a statement accompanying the poll results.

"Employers will have their hands full if a quarter of teens grow up still willing to resort to violence and other unethical behavior when it comes to making decisions about how to settle differences, protect their interests or get ahead," said Miller, who is also author of "God at Work: The History and Promise of the Faith at Work Movement (Oxford University Press, 2006).

There are potential problems with Miller's take on the poll, however.

Teens lie

First, polls can be greatly skewed based on how questions are framed and by how honestly people respond. Adults are known to lie through their teeth in sex surveys, for example. In one Web-based survey, women claimed on average 8.6 lifetime sexual partners. The men claimed 31.9. Some researchers doubt those disparate figures are accurate. A follow-up survey found about 5 percent of each sex said they lied and more than 10 percent said they knew their answer wasn't accurate.

It's reasonable to assume that teenagers, who are prone to prevaricate and whose brains are known to be not fully formed, might fib, knowingly or unknowingly, about heavy questions on topics like violence.

In a telephone interview today, Miller agreed to this possibility, but he cites another question in the poll aimed at getting around this issue: Some 41 percent of the respondents reported a friend had behaved violently toward someone else in the past year. That response, Miller said, is less likely to involve lies.

Words vs. actions

Second, it's also quite possible few of the teens would actually act on the hypothetical responses they gave.

LiveScience's Bad Science Columnist Ben Radford points out that a study of teen virginity pledges, as an example, found that nearly 90 percent of them broke their vow. Another study at Harvard University found that more than half of adolescents who make signed, public pledges on things like virginity and violence give up on their pledges within one year. And in what will not sound ironic to any parent, three-fourths of the teens who pledged not to have sex but did, later denied having made the pledge.

Miller questions whether lying about sexual activity, which may be driven more by hormones than reason, translates to the poll on violence. "We lie about some things, and at the same time, we tell the truth about other things," he said. "Lying in one category does not mean logically we'll lie in others."

Miller also said, regarding words vs. deeds, that today's teens are exposed to exponentially more violence on TV, in video games, in movies, on the Internet, and even in popular extreme sports like kick boxing, "making violent acts seem normative. That's something prior generations didn't have."

Teens grow up

Third, without a similar version of this teen violence poll having been done decades ago, it is impossible to know whether Miller's basic concern — that the state of a teenage mind on such things as intentions and ethics actually predicts adult behavior — holds any water. In fact, science has plenty of evidence to suggest the opposite.

A 2006 study involving questions about how participants (teens and adults) would react to certain situations was, importantly, coupled with brain scans while they answered. Scientists found that teens, frankly, don't care about people's feelings as much as adults do. The part of the brain associated with higher-level thinking isn't fully operational.

Specifically, teens were found to barely use the part of the brain known to be involved in thinking about other people's emotions when considering a course of action.

"Thinking strategies change with age," said neuroscientist Sarah-Jayne Blakemore of the University College London. "The fact that teenagers underuse the medial pre-frontal cortex when making decisions about what to do, implies that they are less likely to think about how they themselves and how other people will feel as a result of their intended action."

The idea of violence in a teen's mind, then, is not likely viewed the same as in an adult mind.

Miller, too, allows that teens change. "Let's hope so!" he said. "All teenagers in all generations go through a stage of boundary testing … and figuring out where the right ethical boundaries are," he told me. "At some level there's nothing new in that. On the other hand, the data is pretty compelling."

Coupled with other data that suggest today's teenagers, and the millennials before them, "tend to embrace ethical relativism, that even as they mature into adults, they will have cultivated habits and brains that are capable of rationalizing behavior that serves their interests, irrespective of traditional societal expectations or understandings of right and wrong," he said.

"I wouldn't overreact" to the survey," Miller said, "but I think to under-react and interpret it as natural youth boundary testing is naive too."

Unethical adults

Lastly, Miller worries not just about violence but that teens will carry their ethical relativism into adulthood. On that point he might be right: A lot of adults have lousy ethics. One need look no farther than the Wall Street Ponzi scheme of Bernard Madoff or the New England Patriots head football coach Bill Belichick's cheating last year for proof.

Bad ethics is not just the purview of the powerful, either. Nearly 20 percent of U.S. adults think cheating on taxes is morally acceptable or is not a moral issue, according to a Pew Research Center survey in 2006. About 10 percent think it's okay to cheat on a spouse.

Cheating is not the same as violence, of course, but if the issue is modern teen ethics, then adults who supposedly grew up in a better era are not necessarily a model to which today's teens ought to aspire.

Robert Roy Britt is the Editorial Director of Imaginova. In this column, The Water Cooler, he takes a daily look at what people are talking about in the world of science and beyond.