Sexy schoolgirls, dirty Disney princesses, naughty Ninja Turtles? When it comes to Halloween, it seems there’s no costume adult women can’t sex up. It’s getting worse every year. And by worse, we mean better. The necklines plunge deeper, the skirts get shorter, the bodysuits get tighter, and we guys are left ogling, wondering just what inspires ladies to transform into tramps for one magical night.

Dr. Natasha Janina Valdez, a relationship and sex therapist and author of A Little Bit Kinky, sees a simple reason. “Because we can… and we can get away with it.” Halloween, like many long-standing holidays and festivals, gives people the opportunity to do things they otherwise wouldn’t for fear of judgment. Dr. Kat Van Kirk, a clinical sexologist, marriage counselor and family therapist, concurs. “There is a lot of pressure on women to conform the rest of the year,” she says, “So when given the chance to dress provocatively with less judgment on Halloween, they do.”

Sort of like how guys go all Batman, Skywalker and Frodo. Fair enough. But what’s with taking un-sexy concepts like “referee,” “SWAT team member” and “health inspector” and slutting them up? Why not just stick to ideas with bona fide sex appeal, like nurses and Bavarian barmaids?

“Women are looking for a variety of ways to express themselves sexually,” says Van Kirk. “That includes taking traditionally masculine roles and costumes and putting a sensual twist on them.” In other words, the tropes of the ancient festivals are back. Halloween provides an opportunity for women to act in ways usually reserved for men, while applying their feminine sexual power to the situation.

But maybe there’s a more basic answer. “That’s what’s readily available,” Valdez says. “All these sexy costumes scream ‘Look at me! I’m hot! Haven’t ya noticed?’ ” Thus, women dress up like a sexy barista not because they have a deep, unfulfilled fantasy to be the girl whose Frappuccino brings all the boys to the yard. They do so because that’s what’s at the costume store.

So, a word of warning. “Be careful what you assume,” cautions Van Kirk. “Not all women dressed as a dominatrix actually have an interest in S&M.” Instead of looking at what a woman is wearing, Van Kirk urges men to look at how she’s wearing it. “Is she confident and comfortable? Or shy and seemingly embarrassed?” She might just be tarted up in the last thing left on the rack, but if she’s rocking it with a winning smile, you’re looking at a lady with a lot of balls. In a good way.

As for how to take that sexy whatever-she-is home, Valdez offers one final tip. “You have a better chance if you’re Jack to her Jill.” Meaning, find out what costumes ladies will be turning out in this Halloween—start with our Sexiest Costumes gallery—then get yourself a complementary get-up. Which, sorry to say, probably doesn’t involve dressing up as a hobbit.