NEW YORK -- The hot spot du jour of Manhattan nightlife looms large over Fifth Avenue and 42nd Street, where crowds of stylish YoCos -- young cosmopolitans -- were jostling inside one evening last week for the right to pay the $15 cover. Rather than crossing the velvet ropes for a rave, house party or disco, the hip patrons here were packing into a controversial lecture at the New York Public Library on the modern meaning of feminism.

"We've both been going to bars and clubs less because events like these are more provocative," said Paul Torres, an MTV producer holding hands with his girlfriend of eight months, IT manager Amy Stemmler, also 30. Recent dates have included a museum crawl at MoMA and a discussion titled "Was the 20th Century a Mistake?" by German director Werner Herzog. "Maybe we'll agree, maybe we won't. But at least we're getting inside each other's heads."

In New York and other northeastern urban centers, including Washington and Boston, gray matter is the new black of the hip social scene. Thousands of young singles and couples are eschewing the perfunctory dinner and a movie for a growing circuit of late-night museum prowls, Oxford-style debates with pre-feud cocktail parties and book readings with cash bars and after-hour bands. In New York, even spelling bee nights have popped up as a romantic twist for the chic, unmarried and grammatically gifted.

It is, observers of the trend say, a visceral backlash to life in a Paris Hilton world. It's a chance to impress a mate, or a potential date, by flexing a body part that has lost ground in recent years to biceps and pecs -- the brain.

"Let's face it, there really is nothing more sensual than caressing someone's mind," said Paul Holdengräber, who launched the library's live lecture series that is now a staple of New York's "intellidating" scene. Two years ago, the average age at library lectures was 68. It is now 41 and falling, driven down partly by a new crop of cutting-edge guests including underground cartoonists Robert Crumb and Aline Kominsky-Crumb and director Jonathan Demme.

"Our ears are a very sensitive place," Holdengräber said, "and lectures give our crowd not only something to listen to, but something to discuss all evening long. You say a lecture isn't romantic? I say but of course it is."

"Intellidating," first coined in England in 2002, sprang from "Intelligence Squared," a live discussion series launched by a couple of British moguls whose professed aim was to make debating "sexy." Heated debates on topics ranging from "Monogamy Is Bad for the Soul" to "Maggie Thatcher Saved Britain" brought in the London glitterati, including actor Hugh Grant and, until their split in February, svelte girlfriend and socialite Jemima Khan.

The concept leapt across the pond to New York last year with the American version of Intelligence Squared -- IQ2US -- launched by philanthropist and businessman Robert Rosenkranz. Housed inside the Asia Society building on the Upper East Side, the popular events have lured a following including conservative pundit Monica Crowley and her boyfriend, the venture capitalist Bill Siegel. The cheaper seats are peppered with budding young brainiacs who find heightened stimulation in verbal joust.

A 45-minute cocktail reception precedes each debate, after which comes a cranial lucha libre where, on one night, author Michael Crichton sparred with other panelists on global warming. For the right set, it can be quite the aphrodisiac.

"The debate itself was far more heated than I'd expected, and Kate and I disagreed completely," said Andy Criss, 28, who took Kate Lauber, a 25-year-old Columbia University American studies major, to an IQ2US debate titled "Is America Too Damn Religious?" for their second date.

Criss said they argued during the 40-minute subway ride back to Lauber's apartment in Upper Manhattan. "It's not like we were just fighting. We were interacting, sharing thoughts, and that was far more satisfying than if we'd gone out to see the movie of the week."

The trend, observers say, is another example of how dating, particularly in the Internet era, is all about niche marketing. With matchmaking Web sites designed for all sorts of people, finding like-minded singles has become easier. Brainiacs are no exception.

A Web site called "The Right Stuff," which advertises that "smart is sexy," bills itself as a place where lonely-heart Ivy League graduates can find their match. intellectConnect.com, a Washington-area company, launched in August 2005 and has built up to 6,000 members, according to co-founder Cindy Embleton.

Over the past two years -- but particularly in the past 12 months -- dozens of cultural institutions have seized on the demand, offering events that draw the intellidating crowd and help the establishments cultivate younger clienteles.

At Housing Works Used Book Café in Soho, Friday night book readings have become lounge-like events with live bands and cash bars. Last year, New York's Museum of Modern Art began PopRally, an event aimed at young couples and singles that mixes cocktails, music and art.

Last month, the Hirshhorn began a series of museum nights with a sold-out event in which 1,700 Washingtonians mingled amid a new installation exploring how artists use light. Revelers heard music spun by garage-style DJ Ian Svenonius and selected to capture the essence of the art. Later, some revelers broke off from the cash bar on an "insomniacs tour" of the galleries.

If Woody Allen were Cupid, one of his romantic inventions might be a New York singles spelling bee night with categories including "sex," "medical conditions" and "uncomfortable things." But he would no longer have to invent it, because Makor -- a Manhattan social center popular with a young, Jewish crowd -- has done it already.

"I just went there to do something fun, but of course, this is Manhattan, and the Jewish community, so everything is really a singles event even if it's not," said Dorron Lemesh, a software writer who attended his first Makor spelling bee three weeks ago.

"One guy had to spell 'chlamydia' and then 'erectile dysfunction' -- and he got both right," Lemesh said. With a chuckle, he added, "But then the women have to worry about a man [who] knows how to spell 'chlamydia.' "