DURHAM, N.H. (AP) -- New research by a University of New Hampshire domestic abuse expert says spanking children affects their sex lives as adults. Professor Murray Straus concludes that children who are spanked are more likely as adults to coerce partners to have sex, to have unprotected sex and to have masochistic sex.

Other studies have shown the link between spanking and physical violence, but Straus said his research is the first to show a link between corporal punishment and sexual behavior.

"My underlying motive was to bring this to the attention of parents and of more people," Straus said, "in the hope it will help continue the decrease in the use of corporal punishment."

Straus, co-director of UNH's Family Research Laboratory, conducted a study in the mid-1990s in which he asked 207 students at three colleges whether they'd ever been aroused by masochistic sex. He also asked them if they'd been spanked as children. He found that students who were spanked were nearly twice as likely to like masochistic sex.

He has bundled that study with three new ones that explore the connections between corporal punishment, coerced sex and risky sex. He presented all four studies this week at the American Psychological Association's Summit on Violence and Abuse in Relationships in Bethesda, Md.

Straus said his study found adults who were spanked as children are more likely to coerce their partners to have sex.

Straus asked 14,000 college students in 32 different countries whether they strongly disagreed, disagreed, agreed or strongly agreed with this statement: "I was spanked or hit a lot before age 12." He also asked whether they had ever verbally or physically coerced an uninterested partner to have sex.

He found a big difference between students who said they'd been hit a lot before age 12 and those who said they hadn't. For every increased step on Straus's four-step scale of agreement, men were 10 percent more likely to have verbally coerced sex from a partner by insisting on sex or threatening to end the relationship if the partner refused. Women were 12 percent more likely to have done that.

Previous studies have shown that 90 percent of parents strike their toddlers, a statistic that's held steady throughout the 30 years Straus has researched corporal punishment. Meanwhile, the number of parents who hit older children has drastically decreased. Straus said it's unclear why, though he has some theories. One is that 2- and 3-year-olds are less likely to respond to repeated verbal warnings.

Straus said he would like more pediatricians and child-rearing experts to warn against spanking. He'd also like lawmakers to take a stand by dedicating state money to teaching parents about the dangers of corporal punishment.

"The best-kept secret in child psychology is that children who were never spanked are among the best behaved," Straus said.

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