File this away under: Things that anyone with two eyeballs could have told you.

A recent study of Washington, D.C., journalists’ Twitter usage found that those who cover the federal government have locked themselves away in “microbubbles” where they primarily talk only to each other. The study suggests that reporters in the nation’s capital “may be even more insular than previously thought,” says its authors, University of Illinois, Urbana-Champaign professors Nikki Usher and Yee Man Margaret Ng.