It's not often that thanks to Victorian-era erotica, a 15-year-old girl experiences a sexual epiphany. But that's exactly what happened to Katherine* during her sophomore year of high school.

When her debate team stopped at a bookstore on an out-of-town trip, a friend purchased a book of 19th century sex stories. You know what happens next: on the bus ride home, a wide-eyed Katherine pored over one tale about a man and his female servant.

This sexcapade, though, had a special twist: it involved a lot of spanking.

"I thought, 'Oh my God, this is an actual thing! I'm not the only one who thinks this is interesting!'" Recalls Katherine, a 41-year-old photographer in New Mexico. She's thought about spanking since she was a little girl, but it wasn't until she became aroused reading that story that she wanted to be spanked by a man in bed.

Women like Katherine aren't alone: lots of people are into love taps—over-the-knee or tangled up in intercourse, one item on the foreplay buffet or the main event. "For some people, a good hard smack is going to bring nerve endings to life," says Dr. Yvonne Fulbright, sexologist and author of Touch Me There: A Hands-On Guide to Your Orgasmic Hot Spots.

It's tricky to find out how many people are doing it, but you don't have to look further than pop culture to see we've got spanks on the brain: paddlings make appearances everywhere from old episodes of I Love Lucy to the 2004 flick Along Came Polly to Broadway's hit show Spring Awakening. Back in 1996, essayist Daphne Merkin shocked New Yorker readers with a frank article about her desire to be spanked by a man; even Justin Timberlake promised in his 2006 single SexyBack, "I'll let you whip me if I misbehave." (Were you talking to Britney, Cameron, or Jessica when you said that, Justin?)

The posterior is full of its own nerves, and the bum is also located near the body's sensory hot spots—a man's scrotum and a woman's vulva. A naughty maneuver like spanking is a great way to send ripples through the skin and stimulate that entire area, Fulbright says.

Thomas Roche, a 39-year-old erotica writer in San Francisco, says spanking is "hot, emotionally charged and so intimate" all at once. But for him, the allure of spanking a woman is all the "bodily contact"—a submissive woman's rear end and all the parts around it.

Spanking is appealing to different folk for different reasons. "Some people like the punishment, role-playing thing, some people just like the spanking part of it. For some people, it's more innocent," says Rachel Kramer Bussel, editor of Spanked: Red-Cheeked Erotica, who wrote passionately about her love of a good spanking in her former Village Voice sex column. "You have to figure out what part of it you're interested in exploring so you can explain it to the other person."