C Thi Nguyen:

An ‘epistemic bubble’ is an informational network from which relevant voices have been excluded by omission. That omission might be purposeful: we might be selectively avoiding contact with contrary views because, say, they make us uncomfortable. As social scientists tell us, we like to engage in selective exposure, seeking out information that confirms our own worldview. But that omission can also be entirely inadvertent. Even if we’re not actively trying to avoid disagreement, our Facebook friends tend to share our views and interests. When we take networks built for social reasons and start using them as our information feeds, we tend to miss out on contrary views and run into exaggerated degrees of agreement.

An ‘echo chamber’ is a social structure from which other relevant voices have been actively discredited. Where an epistemic bubble merely omits contrary views, an echo chamber brings its members to actively distrust outsiders. In their book Echo Chamber: Rush Limbaugh and the Conservative Media Establishment (2010), Kathleen Hall Jamieson and Frank Cappella offer a groundbreaking analysis of the phenomenon. For them, an echo chamber is something like a cult. A cult isolates its members by actively alienating them from any outside sources. Those outside are actively labelled as malignant and untrustworthy. A cult member’s trust is narrowed, aimed with laser-like focus on certain insider voices. In epistemic bubbles, other voices are not heard; in echo chambers, other voices are actively undermined.