BROOKE GLADSTONE:  The year was 1999. The Daily Show sent Stephen Colbert to the UK to report on a groundbreaking new technology.

  [CLIP]:

STEPHEN COLBERT:  Gaydar, the brainchild of a young inventor from Surrey, England.

  [AUDIENCE LAUGHTER]

STEPHEN COLBERT:  What is Gaydar?

DAVID ELIOT:  Gaydar is a small device which helps gay men or women meet in the streets. This sends a frequency to your one, and your one sends a frequency back to mine, which makes mine vibrate.

STEPHEN COLBERT:  And that’s your way of telling me you’re gay.

DAVID ELIOT:  That’s right, yeah.

  [BEEPS/AUDIENCE LAUGHTER]

  [END DAILY SHOW CLIP]

BROOKE GLADSTONE:  Fast forward a decade to 2009 and the release of the smartphone called Grindr, still the most successful location-based discovery app, with more than six million users worldwide, most of them gay and bisexual men. The app recently celebrated its fourth anniversary and it's the subject of a new book titled. Meet Grindr:  How One App Changed the Way We Connect. Author Jaime Woo says that the technology that made Grindr possible arrived in 2008, with Apple's release of the GPS- equipped iPhone 3G.

JAIME WOO:  Grindr was one of the first apps to really use this GPS capability on smart phones. What you’re gonna see is a grid, and you have little thumbnails of all the different guys who are around you. And they’re sorted by proximity, the closest user at the top and then the farthest at the bottom. And in many cities, that would be maybe 100 men within a thousand feet.

BROOKE GLADSTONE:  What if you're using Grindr in Montana?

JAIME WOO:  Yes, I think the least populous state for Grindr is North Dakota, with about 400 users. And I think there it’s a  opportunity to feel some kind of kinship I think it ends up being more like a traditional online dating site then because you just can't pick up and go see that person very quickly, but you can still chat with them.

BROOKE GLADSTONE:  Which brings us to what exactly Grindr is for, and it's not exactly to – you know, find a knitting circle.

JAIME WOO:  You know, you never know. People might use it that way. When I was introduced to Grindr, it was described to me by my friends as a cruising app, and that means that it’s an app that was used to help men find casual sexual encounters. There was a survey that was done for 18- to 24-year-old men in the West Hollywood, California area, and they asked the survey respondents what they were using Grindr for. Hooking up was the main reason. But once they were asked for top reasons, rather than just one reason, we saw that men were looking for friends, they were looking for dates, they are looking to break into the LGBT community. And so, we see that people are using it for different reasons, in addition to hooking up.

BROOKE GLADSTONE:  Now, the premise of your book is that Grindr significantly changed gay culture. How?

JAIME WOO:  It gave people a chance to take an activity - trying to find other men for sex - and take it with them anywhere that a Wi-Fi or a data signal exists. So they can be on a road trip from one city to another and see all of the queer men along the way. And that's very different, because previously we had to depend on either a bar or you’d have to go to a website to find it. But Grindr gave us real-time spontaneous results.

BROOKE GLADSTONE:  What about the straight community, is there something like that for them?

JAIME WOO:  You know, they’ve been trying to crack this egg for so long. Every month there seems to be another app that's trying to do this. And in the book, I discuss a couple of reasons why I think that it hasn't quite been so successful. Part of it is just that there has been a historical tradition of cruising in the queer community. I think there’s a safety concern here, especially for women. Certainly, whenever I hear from women on online dating sites, there is a risk of being swarmed or feeling  unsafe.

BROOKE GLADSTONE:  But you also say the real-life dating rituals among straight people are different.

JAIME WOO:  When you're in high school, you learn the first date, the second date, the third date ritual and, as you get older, marriage is this firm goal. When we see apps that are for straight people, they parallel the dating process.

BROOKE GLADSTONE:  Like the first time you meet someone on OkCupid, you have a coffee, and then you move on to dinner or something like that.

JAIME WOO:  Or they'll do a matching game with they say these five people may have looked at your profile, try to guess who saw you recently, answer these questionnaires and see if the other person will match up with you? Grindr strips that all away. Grindr says, this is a person, do you find them attractive, do you want to meet? Grindr puts all of the emphasis on gauging compatibility and chemistry in-person.

BROOKE GLADSTONE:  Certainly, being able to find a community easily is a good thing, but you also have some problems with its impact on the culture.

JAIME WOO:  Absolutely. The main frustrations that we hear about Grindr and other hook-up apps is that it can be quite exclusionary. So they will say, no fatties, no baldies, no Asians. The thing about the design of the app was that with just one photo and 120 characters to describe yourself, it could exacerbate conforming to the cultural standard of beauty and having people really select for the images that they see in magazines and in advertisements.

BROOKE GLADSTONE:  Young, thin, white? That standard has bedeviled gay and straight culture for a very long time.

JAIME WOO:  Yes. I think what we're seeing though is that the culture is changing. The percentage of mixed race relationships and marriages is climbing year upon year, and slowly we’re starting to see in our media representations of different faces and different body sizes. What we’re seeing is maybe just a lag with the queer culture, where they haven't really thought about this quite as much as straight culture has.

BROOKE GLADSTONE:  What do you think the future of this kind of app could be, outside of dating and sex?

JAIME WOO:  I'm a big fan of Samuel Delany, and in his book, Times Square Red, Times Square Blue, he discusses this concept of contact and networking. Networking is where there’s a functional role to the people in our lives, to help support our careers or support or hobbies. Contact, on the other hand, are kind of those encounters that we have that are ephemeral - that fleeting conversation we have in the park - that don't necessarily impact us in a direct way in our careers but that kind of human interaction that brings some joy to us. I think that that's what the discovery apps are trying to do. They’re trying to bring in a form of contact, where we can meet other people and have those ephemeral moments. LinkedIn and Facebook and Twitter all about networking. So I wrote this book, not just for the queer community. I want to see more contact in our lives.

BROOKE GLADSTONE:  Jaime, thank you very much.

JAIME WOO:  Thank you.

BROOKE GLADSTONE:  Jaime Woo is the author of Meet Grindr:  How One App Changed the Way We Connect.