THERE are nearly four million single people in New York City. A number of them are not as original as they think.

New data from a Web site suggests that not only do many people plan similar dates, but like lemmings, they also collectively migrate from one theme to the next.

In March, scores of New Yorkers opted to have their first dates over tacos: fish tacos, dried cricket tacos, taco tours of Brooklyn, even post-surfing tacos at Rockaway Beach in Queens.

But by month’s end, tacos went out of vogue, and fondue became the fare of choice for first dates. In mid-April, singles relinquished their cheese forks and embraced bring-your-own-beer dates instead. A few weeks later, outings for lobster rolls were all the rage. By mid-May daters cooled on lobster rolls and were eating oysters.

“It was with taco dates that we first started noting that certain types of dates came in waves,” said Brian Schechter, a founder of HowAboutWe.com, a nascent dating Web site that began fostering love connections in the spring. Mr. Schechter created the site with his best friend since kindergarten, Aaron Schildkrout.

The entrepreneurs, both 31, are former charter-school teachers who practiced meditation in India and taught at meditation retreats in the United States. They did not set out to track the dating habits of New Yorkers, let alone suggest that there could be a collective dating unconscious. They simply wanted to create a new kind of dating site where members could demonstrate who they are, not with personal essays and awkward messages, but by proposing dates that begin with the words: “How about we. ...”

Yet since HowAboutWe logs thousands of dates from some 7,000 young New Yorkers — the average age on the site is 29 — it has opened a window onto dating in the city and turned Mr. Schildkrout and Mr. Schechter into accidental anthropologists.

At a reporter’s request, they sifted through thousands of dates to identify where singles rendezvous. It was hardly scientific, though their 10,000-date sample size was larger than the ones used in many sociological studies.

Tucked into a sunny booth in V Bar in the West Village, Mr. Schechter pushed aside a panini and flipped open a laptop, revealing a spreadsheet of dates proposed and accepted by the site’s members: “How about we attend a swing class and wine tasting?,” “How about we grab a beer and play a game of ping-pong at SPiN?,” “How about we check out Ninja New York, a Japanese restaurant with ninjas for waiters in the meatpacking district?”

“You can tell so much about somebody based on the date they propose,” Mr. Schildkrout said.

Both he and Mr. Schechter have profiles on HowAboutWe. Mr. Schechter’s page says he possesses obscure knowledge about chakras. His latest date proposal? “How about we learn how to read tarot cards (after buying a set somewhere in Manhattan) and practice at the 169 Bar?”

Scanning the site’s database, he observed, “There are trends and hot spots.”

Indeed, Coye Cheshire, an assistant professor at the School of Information at the University of California, Berkeley, said strangers have been shown to gravitate to the same things at the same time as preferences are diffused among groups through word of mouth or social networks. “It’s not surprising to see these trends ebbing and flowing,” he said.

Samuel D. Gosling, a psychologist at the University of Texas at Austin, said that the cuisine trends could occur because members of the Web site value doing the latest thing — until it becomes widespread. (After all, they were early adopters of the site itself.)

“It might be that you only want to do it if 1 percent of other people are doing it,” he said. “You don’t want to miss the trend, but you don’t want to be behind the edge. That sort of decision strategy would result in that pattern.”

That New Yorkers on a dating site would be drawn to similar activities can be explained in part by a sociological principle known as homophily. “It’s the idea that similar people tend to value the same things as other people like them,” Professor Cheshire said.

He and colleagues at Berkeley have studied countless online dating profiles and observed that while people think their tastes are distinct, most everyone’s profile says they like fine dining, movies and long walks on the beach.

“What’s interesting about it is the way that we try to show that we’re special and unique is that we like to do things just like everybody else,” Professor Cheshire said with a chuckle.

Proposing a date can also be a form of social signaling. “You’re trying to signal that you’re somebody who’s at the cutting edge,” said Eli J. Finkel, an associate professor of psychology at Northwestern University.

Catherine Bartolomeo, 22, a member of HowAboutWe who has suggested hunting for the best cup of coffee or going to Film Forum, likened date proposals to advertising.

“You try to portray your personality in a few short words,” she said. “ ‘Let’s go for drinks!’— that’s boring. You don’t want to be on a date with a brick.”

Mike Chang, 31, a technology consultant who has proposed “bar Olympics” dates in which Skee-Ball is a sport, said humor is crucial.

“If someone says something like ‘Let’s go walk the High Line and look for people with mullets,’ you think, ‘I’ll have a better chance of having fun with this person doing this activity than the person who just says ‘Let’s go walk the High Line.’ ”

Often, there are more men than women on dating sites. HowAboutWe has a 60-40 female-male split, and Mr. Schildkrout said he thought “the girls’ dates are a little more specific and creative.”

Alyssa Frazier, 26, who works in marketing and is a member of the site, agreed. “One guy wants to recreate ‘Ferris Bueller’s Day Off,’ ” she said, “but I definitely think girls come up with the more creative things to do.” She proposes dates for things she would rather not do alone, like attending food and wine pairing classes and standing in line at Shake Shack.

After analyzing thousands of dates, Mr. Schildkrout and Mr. Schechter identified the most popular categories, including foodie, dance, games, make-believe and prankster dates.

“Make believe” dates include things like “How about we pretend to be a couple and take a tour of the French Culinary Institute as ‘prospective students?’ ” The “prankster” category includes gems like “How about we go to a free marriage counseling session with a priest knowing nothing other than each others names?” and “How about we go to a library or bookstore and leave notes inside books?”

Such proposals, Mr. Schechter said, serve as a mating call for quirky singles. “These are, ‘I’m a weird person and if you’re weird too, we could get along.’  ” (Site members said they happily attempt the unconventional dates. The most bizarre ideas, however, are understood as displays of drollness.)

There is the “artistic” date: attending a pottery class or collaborating on a sidewalk chalk drawing. And there is the “cool hunting” date, where the structure of the outing is “let’s go find the best margarita.”

Obviously dating trends also undulate around the seasons as well as major New York happenings, like concerts.

HowAboutWe members fill out profiles consisting of photographs and factoids under headings like “One thing my mother would want you to know about me,” but they primarily interact around the dates they propose.

The site is free, though to send unlimited messages to potential paramours there is a fee (the best deal is $48 for six months). Upon joining, you are asked to rate a series of date ideas, which helps the site’s algorithm determine your matches. Next, you are shown a list of members and their date suggestions. You can then send a member a message or conduct a search. For instance, you can search for women 25 to 35 who want to attend the Hester Street Fair. (There are three.)

And if glazing pottery or ascending the Empire State Building sounds as if you would spend an inordinate amount of time with someone you might never care to see again — it may be.

“I’ve had some disaster dates,” Ms. Bartolomeo confessed.

But she is undeterred. “You’re still doing something you want to do,” she said. “Even if it’s not someone you want to do it with.”

Copyright. New York Times Company. 2010 All Rights Reserved.