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What your metadata says about you

From MIT’s César Hidalgo, a new window on what your e-mail habits reveal

César Hidalgo (left) with Daniel Smilkov and Deepak Jagdish at the MIT Media Lab.Barry Chin/Globe Staff

As recently as a few weeks ago, “metadata” was an obscure term known mainly to techies and academics. Broadly defined, metadata is data about other data. For the phone company, it might be the time and length of your calls, but not the conversation itself; in the context of e-mail, it means information such as the sender and recipients of a message—basically, everything except what the message actually says.

Then came the revelation that the National Security Agency has been collecting metadata about millions of Americans’ phone calls. Suddenly metadata exploded as a public issue. Is it a harmless way for the government to track dangerous patterns or a tightening net around our lives?

For César Hidalgo, this national conversation about metadata couldn’t come too soon. A professor of media arts and sciences at the MIT Media Lab, Hidalgo has been obsessed with communications metadata for years. To him, metadata isn’t merely a technical issue, or a political one, but an emotional one—a cloud of knowledge about your behavior that, once you confront it, can literally change your life.


To make metadata more visceral, he and a group of graduate students are launching a new online project to help people visualize their own metadata, or at least one small corner of it. The program, called “Immersion,” asks users for their Gmail address and password; it then scans every e-mail in their accounts and scrapes the metadata to create a portrait of their personal network. With the circles and lines of a network diagram, it highlights the 100 people with whom you’ve communicated most, and shows how closely they’re connected to you and how thickly interconnected with one another in your mailbox. Unlike Google, or the NSA, the project also offers an instant deletion option: Remove your name, and it erases your metadata.

The project has already been running in beta form in the Media Lab lobby, and about 500 people have run their networks. Some people have one key person in their inbox, creating a huge circle like the star in a solar system; some people have what Hidalgo calls “the George Costanza”— two distinct clusters of contacts that rarely interact (“Worlds are colliding! George is getting upset!”); and so on. The images are abstract, but once you get a handle on what they mean, it’s eye-opening to see the topography of your personal web.


The project goes public June 30. Users can sign up at Hidalgo spoke with Ideas from the Media Lab.

IDEAS: Should we really see emotional meaning in metadata?

HIDALGO: All of this data is about people. Data basically doesn’t make sense without humans. It’s a very human construct, and, in the past, most of our data was not about people. We had astronomical data, we had a lot of data about animal species or data about materials and their properties.

But more and more, recently, all of this metadata is collected, originally for operational purposes. Whether it’s e-mail data or financial-transaction data, it all involves people. But, more than that, it involves interactions between people. And that’s why I think metadata has this emotional component: because ultimately, those interactions are the ones that we associate emotions with.

IDEAS: When you first saw your own e-mail metadata mapped out, what did you feel?

HIDALGO: When you see it all together, it is, in a way, an out-of-body experience. You’re seeing all of your network and you’re seeing yourself out of it and you’re seeing it from afar and you’re seeing it in one picture.

You start realizing that, eventually, you are not interacting with people—you’re interacting with webs of people. Because all the people you’ve interacted with, they’re actually connected in tens or maybe hundreds of indirect paths between them. They exist in your absence. So that out-of-body experience, I’ve found that it was very powerful.


IDEAS: How do you feel about the way metadata is being discussed since the NSA revelations?

HIDALGO: It’s like the world is catching up to what a fringe group of academics was aware of in 2004 and 2005. Nobody liked [thinking about metadata], and nobody cared about us, and they all thought that working with mobile phone records or e-mails was sort of a curiosity or a stupidity. And we’ve come to a world where, now, it’s completely the opposite. Everybody’s chasing that. So, for me, I think it’s healthy that these kinds of [news stories] come out, because it helps everybody start having conversations that are rich, that are important.

IDEAS: Are there ethical or political lessons about metadata that Immersion teaches?

HIDALGO: What I believe is, if you’re going to make platforms that deal with personal data, you have to develop ways of doing this in such a way that you can be transparent with the user about the data you have, about how you’re handling it, and about how the user can withdraw the data from your system. And I think we don’t have that [in society], because what happens is, all of these things are buried in these user agreements that are longer than the Constitution....Hopefully, [with our deletion policy], we can lead by example, by showing that, when it’s possible to build these platforms, it may be something that people appreciate. It’s a very simple feature on the platform, but it makes a very strong moral point about the way we should deal with data.


IDEAS: How can seeing your own communications metadata change your life?

HIDALGO: If you see a movie where generals are planning a war, they have a little map and little toy soldiers, and that’s how they move around. They don’t have a view of how soldiers see things on the ground. They have this view that is more of a bird’s-eye view, a view from afar. The platforms that we have now, like Facebook and Twitter, provide us a stream—but that stream is not a map. It’s like looking out the car window, but it’s not like looking at the GPS.

From that perspective, I think [metadata visualization] allows us to think a little bit more about who you connect to and why. Are we having healthy relationships? Are there parts of our networks that maybe we’d like to grow more? Are there parts of the network that we’d like to connect with other parts of the network that we have not yet done so?

I do not believe that just connecting more is better. That’s overly simplistic, and I don’t think anybody truly believes that. Eventually, it’s not about having more connections but about having the right connections.

IDEAS: Would the world be a better place if everyone had access to all of their own communications metadata?


HIDALGO: I do think that it might be a world that we want to give a shot. I’d want to explore the opportunity.

To participate in the Media Lab’s “Immersion” project, visit

Abraham Riesman is a writer and documentary filmmaker in New York City. You can see his work at