Negative results are the bane of scientists. Virtually all of them will never be published despite the fact that one can mine some interesting nuggets in there. In my own experience, the experiments would yield negative results probably 90% of the time. That's a fair bit of unrewarded work that no one outside of the lab will likely know about. As long as the scientists include good controls, there is no reason--other than lack of sexiness--that negative results should remain unpublished. I think the solution that the study's authors proposed, a negative results repository, should be created for all the sciences.