A psychology study published recently in the Proceedings of the National Academy of Science has shown that political messages on social media containing “moral and emotional language” diffuse far faster than political posts on more morally neutral topics.

For example, an impassioned rant about proposed gun control legislation is much more likely to “go viral” than an evenhanded analysis of the effects of cutting interest rates in the current economic climate.

More interesting is the study’s secondary finding. Political posts rich in moral and emotional content may spread faster and wider than other kinds of political messages – but very rarely so wide as to penetrate the conversation on the other side.

Pundits have long warned of social networking’s tendency to create “ideological echo chambers,” which constantly reinforce users’ existing beliefs while insulating them from arguments on the other side. Indeed, most people can attest to the effect themselves from a glance over their own newsfeeds. But, until now, there has been little empirical grounding for these concerns.

The proof is important because without it, it was all too easy to dismiss the worriers as heirs to a long tradition of doomsaying when a new medium of expression gains a large, young following. Television was debasing popular and political culture before the internet, and the radio before TV, etc. – the pattern stretches back to the printing press. Yet if these findings are correct, this moment is different.