They misreport their experiments and don’t fess up when they’ve been caught.

Javier Benitez points us to this paper, “COMPare: Qualitative analysis of researchers’ responses to critical correspondence on a cohort of 58 misreported trials,” by Ben Goldacre, Henry Drysdale, Cicely Marston, Kamal Mahtani, Aaron Dale, Ioan Milosevic, Eirion Slade, Philip Hartley and Carl Heneghan, who write: Discrepancies between pre-specified and reported outcomes are an important and …