Emerson GB, Warme WJ, Wolf FM, et al. Testing for the presence of positive-outcome bias in peer review: a randomized controlled trial. Archives of Internal Medicine 2010;170(21):1934-1939. (doi:10.1001/archinternmed.2010.406)
Two versions of a randomized controlled trial that differed only in the way the main finding was described (positive finding or no difference) were peer reviewed by 210 reviewers of two journals (The Journal of Bone and Joint Surgery and Clinical Orthopaedics and Related Research). Three forms of positive-outcome were observed: reviewers were significantly more likely to recommend the positive version for publication; they detected more errors in the no-difference version; and they awarded higher methods scores to the positive version, even though the two versions had identical methods sections.