BOB GARFIELD: This is On the Media. I'm Bob Garfield.

BROOKE GLADSTONE: And I'm Brooke Gladstone. Every once in a while we examine words or phrases that have been percolating in the media, and the phrase that's been bubbling up lately is "echo chamber." It used to mean a room with hard reflective walls, a speaker and a mike. But now it's mostly a metaphor. Cass Sunstein is a professor at the University of Chicago Law School and author of Republic.com. He says the phrase can be applied to a wide array of cultural reverberations.

CASS SUNSTEIN: Sometimes what's meant by echo chamber isn't something completely new. It's like a rumor mill, and the idea is that if you have an idea or a claim about a fact that's repeated over and over again, then it will start to assume reality. Sometimes and it may be a little more interesting, the echo chamber is narrower -- to some part of the citizenry. Say, liberals will all hear one thing echoing, and conservatives will hear another thing echoing, and they'll be very different things, so people will in a way live in different social realities, just because they hear such different claims about the facts.

BROOKE GLADSTONE: And there are some media watchers who call this manifestation of the echo chamber "incestuous amplification."

CASS SUNSTEIN:Yeah. The term "incestuous amplification" is often a military term, and it's used there as a warning against military leaders who keep talking to each other as if they're in a family, and then they don't watch out for things that can go wrong. And so incestuous amplification sets a recipe for disaster. That military idea has a lot of parallels for completely non-military groups, like companies like Enron where there wasn't much dissent --people were just echoing one another's optimism in a way that led to disaster, and in terms of sometimes government behavior when there's incestuous amplification for a domestic policy that goes sour and might not have if people who lived outside the echo chamber have had a chance to speak to the people who live in it.

BROOKE GLADSTONE:Let's talk about the echo chambers that you specialize in. These are the chambers that exist, both small and large, in cyberspace.

CASS SUNSTEIN: Yeah. The internet has many great advantages from the standpoint of democracy, 'cause people can expand their horizons, but one thing that's happened is that many people use the internet to narrow themselves, so that they end up speaking mostly to people who already agree with them. So one just fact about the operation of the internet is you get these Dean supporters, for example, speaking most of the time to fellow Dean supporters, and the same can happen for Bush supporters who hear only what other Bush supporters say about the Democrats or about France. And the internet really facilitates a situation in which people are in a way living in echo chambers that they themselves have created.

BROOKE GLADSTONE:And this phenomenon you've applied a new term to called "cyber cascade." Does that relate to incestuous amplification only it's on the web?

CASS SUNSTEIN: Yeah. Cyber cascades are specifically a web phenomenon in which one fact or something that's supposed to be a fact is stated to another person who then tells maybe another dozen people who then tell maybe another 10,000 others, and pretty soon people all over the world are hearing and potentially believing something that just isn't so.

BROOKE GLADSTONE:At the risk of being obvious, state for the record what you think the long term impact of the proliferation of these echo chambers would be.

CASS SUNSTEIN: The greatest danger of the echo chambers is unjustified extremism. So it's a well-known fact that if you get a group of people who tend to think something, after they talk to each other, they end up thinking a more extreme version of what they thought before, and the danger of that is you can make a situation where mutual understanding is, is difficult, and people don't appreciate but instead demonize those who disagree with them. And that's an ongoing threat to our democracy.

BROOKE GLADSTONE: So beware the echo chamber?

CASS SUNSTEIN:Yeah. If it turns out that we're talking mostly to people we agree with, something's gone wrong, and there's a kind of obligation for citizens to leave their echo chambers at least some of the time and seek out dissenting opinions.

BROOKE GLADSTONE: Okay. Cass Sunstein, thank you very much.

CASS SUNSTEIN: Thanks for the questions. Great. Thanks a lot.

BROOKE GLADSTONE: Cass Sunstein is a professor at the University of Chicago Law School and author of Republic.com.

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