A new paper in the Journal of the European Economic Association, published by Oxford University Press, indicates that we tend to listen to people who tell us things we’d like to believe and ignore people who tell us things we’d prefer not to be true. As a result, like-minded people tend to make one another more biased when they exchange beliefs with one another.

Source: People only pay attention to new information when they want to

Social media delivers to us much information whose credibility is unknown.

The researchers find we evaluate unknown sourced information based on whether it agrees with our existing thoughts. We judge information we agree with (even if factually wrong) as more credible merely because it aligns with our pre-existing thoughts.

Explains also why social media propaganda echo chambers act to amplify existing biases.