Welcome to this special issue on Negative Results in Software Engineering. First, what do we mean by negative results? Negative or null results-that is, results which fail to show an effect-are all too uncommon in the published literature for many reasons, including publication bias and self-selection effects. Such results are nevertheless important in showing the research directions that did not pay off. In particular, "replication cannot be meaningful without the potential acknowledgment of failed replications" (Ferguson and Heene 2012).
Negative Results in Software EngineeringWe believe negative results are especially important in software engineering, in order to firmly embrace the nature of experimentation in software research, just like most of us believe industry should do. This means scientific inquiry that is conducted along Lean Startup (Ries 2014) principles: start small, use validated learning and be prepared to 'pivot', or change course, if the learning outcome was negative. In this context, negative results are, given their methodology, failed approaches that are just as useful as successful approaches: they point out what hasn't worked, in order to redirect our collective scientific efforts. As Walter Tichy writes in Tichy (2000), "Negative results, if trustworthy, are extremely important for narrowing down the search space.