NASHVILLE, TN - AUGUST 28: Running back Adrian Peterson #28 of the Minnesota Vikings looks on during a preseason game against the Tennessee Titans at LP Field on August 28, 2014 in Nashville, Tennessee. (Photo by Ronald C. Modra/Sports Imagery/ Getty Images)

Following the news that Minnesota Vikings running back Adrian Peterson reportedly used a tree branch to hit his 4-year-old son (and the later accusation that he injured another 4-year-old son), the acceptability of physical punishment has been a topic of national conversations.

Some Internet commenters and even other athletes have defended Peterson -- many arguing, "I was spanked and I turned out OK!" Others admit they're in support of spanking, but recognize Peterson's behavior as abuse.

A poll conducted by The Huffington Post and YouGov found that 81 percent of 1,000 adults polled believe spanking with a hand should be legal, and almost half think it's an effective form of punishment.

Indeed, whether the respondents' own parents used corporal punishment made a big difference in their views about the legality of spanking. Eighty-eight percent of those whose parents used corporal punishment, but only 69 percent of those whose parents did not, said spanking with the hand should be legal. Peterson has justified his behavior by saying he believes he is successful because of the way his parents disciplined him.

However, there is overwhelming evidence that physical punishment is both ineffective and harmful to child development. Former HuffPost Senior Columnist Lisa Belkin has argued that the word "debate" should be left out of the spanking conversation, because the science against it is so clearly one-sided.

"There aren't two sides. There is a preponderance of fact, and there are people who find it inconvenient to accept those facts," Belkin wrote in a 2012 column.

Psychologist Elizabeth Thompson Gershoff has spearheaded multiple studies on the topic, all of which have supported her 2002 conclusion that it has vast negative effects. At the time, Gershoff had analyzed more than 80 studies and found there was a "strong correlation" between corporal punishment and negative behaviors (including increased aggression and antisocial behavior).

Here's a breakdown of what science has to say:

Physical punishment makes kids more aggressive.

Researchers from Tulane University found that children who are spanked frequently at age 3 are more likely to show aggressive behavior by the time they're 5 than kids who are not.

Physical punishment doesn't actually work (even if it appears to).

Yes, spanking may stop problematic behavior, says Sandra Graham-Bermann, Ph.D., a psychology professor and principal investigator for the Child Violence and Trauma Laboratory at the University of Michigan, but that's because the child is afraid. In the long term, physical punishment will only make kids' behavior worse.

Reporting on several studies on the topic for CNN, Sarah Kovac wrote, "The sad irony is that the more you physically punish your kids for their lack of self-control, the less they have. They learn how to be controlled by external forces (parents, teachers, bosses), but when the boss isn't looking, then what?"

Physical punishment encourages kids to continue the cycle of abuse.

A 2011 study published in Child Abuse and Neglect confirmed that physical punishment is cyclical -- children who are hit are more likely to use the action to solve problems with their peers and siblings.

Later on, they're at a higher risk for delinquency and criminal behavior, according to a 2013 article, "Spanking and Child Development: We Know Enough Now to Stop Hitting Our Children," also by Gershoff.

The negative effects of physical punishment are colossal, well into adulthood.

A 2012 study published in the journal Pediatrics found that "harsh physical punishment was associated with increased odds of mood disorders, anxiety disorders, alcohol and drug abuse/dependence, and several personality disorders."

A review published in the Canadian Medical Association Journal that same year analyzed 20 years of data and came to similar conclusions regarding those risks -- and also found that spanking yields no positive outcome.

Spanking actually alters kids' brains.

A 2009 study concluded that children who were frequently spanked (defined as at least once a month for more than three years) "had less gray matter in certain areas of the prefrontal cortex that have been linked to depression, addiction and other mental health disorders."

According to CNN, another study -- also looking at how corporal punishment affects the brain -- found that children who receive it have a decrease in cognitive ability, compared with other kids.

The bottom line:

Stacy Drury, a professor of psychiatry and behavioral science at Tulane University, told the New Republic, "The goal of discipline, which actually comes from the Latin root meaning 'to teach,' is to change behavior. And physical discipline across many, many, many studies is ineffective at changing behavior and it’s ineffective for many reasons ... corporal punishment actually teaches children is that aggression is an acceptable method of problem solving."

The HuffPost/YouGov poll was conducted Sept. 15-17 among 1,000 U.S. adults using a sample selected from YouGov's opt-in online panel to match the demographics and other characteristics of the adult U.S. population. Factors considered include age, race, gender, education, employment, income, marital status, number of children, voter registration, time and location of Internet access, interest in politics, religion and church attendance.

The Huffington Post has teamed up with YouGov to conduct daily opinion polls. You can learn more about this project and take part in YouGov's nationally representative opinion polling. Data from all HuffPost/YouGov polls can be found here.