A new U.S. study that has drawn criticism from rights advocates says children who are spanked may grow up to be happier, more productive adults.

Researchers at Calvin College, a Christian school in Michigan, surveyed 2,600 people and included interviews with 179 teenagers. They concluded that children spanked by their parents may perform better at school and grow up to be happier than those who don't receive such punishment.

Teenagers who were spanked up to age six reported that they were more successful in school, more interested in attending university, more likely to work as volunteers and more positive about life, the researchers say.

Psychologist Marjorie Gunnoe, the study's lead researcher, interviewed people between ages 12 and 18. The study examined their responses on a questionnaire concerning how they were disciplined as children, and compared the responses to their conduct as teenagers.

The study, which hasn't been published yet, focused on a number of "good" and "bad" behaviours, such as optimism about the future and anti-social conduct. Teenagers who were spanked between two and six years of age performed slightly better on the positive behaviours -- but no worse on the negative measures -- than those who had never been spanked.

Another finding was that young people who were still being spanked when they were in their teens, displayed behavioural problems.

The study was not intended to encourage parents to strike their children, Grunnoe reportedly said, but to dissuade government from banning the practice.

However, Grant Wilson, president of the Canadian Children's Rights Council, criticised the study and said spanking should be banned.

"Canada is a country that should have eliminated this quite a while ago," he told CTV News Channel. "If you look at the polls, parents are generally speaking against hitting children for the purpose of disciplining them."

"It is contradictory to say to a child 'it's ok for a parent, a big person, to hit you and cause you physical pain,' and then 'you should go out and play with your friends and not hit them,'" he said.

However, Andrea Mrozek, with the Institute of Marriage and Family Canada, said spanking children can be positive if used "appropriately."

"There's a certain age range where it's appropriate and in fact may even be necessary to prevent greater harm to a child," Mrozek said.

"When you have legislature step in and tell parents how to be parents, I think it's extremely detrimental," she added.

Spanking is prohibited in many countries, particularly in Europe. It's legal in the U.S. and Canada, under certain circumstances.