A recent news piece in Nature reported in glowing terms on the “first analysis of ‘pre-registered’ studies”, stating that “[pre-registration] seems to work as intended: to reduce publication bias for positive results.” There are reasons to be somewhat dubious about this claim.
The analysis in question appears in a preprint, “Open Science challenges, benefits and tips in early career and beyond”. The analysis is a small part of the paper, occupying about half a page of an 11-page document. The paper draws no strong claims from the data; the Nature story goes well beyond what the paper says, though I can easily believe the authors waxed proudly about their results when interviewed by the journalist.
The preprint is really an essay on preregistration and true to its title discusses challenges and risks, esp. for early stage investigators, as well as potential benefits. The authors are proponents of preregistration and reach the expected conclusion that the benefits outweigh the risks.
The angle of the Nature story is that preregistration cuts publication bias by increasing the proportion of null results that are published. The reporter drives the point home with a graphic (reproduced below) that vividly shows the increase in null findings in bright red: 55-66% with pre-registration vs. 5-20% without. Sounds convincing.