A nice little dust-up is happening in neuroscience right now: An experimental neuroscientist claims that we should not waste our time replicating published results. Why? because:
"unsuccessful experiments have no meaningful scientific value."
Richard Tomsett goes through the piece here: Are replication efforts pointless? And Neurosceptic has a good take-down too: On "On the emptiness of failed replications"
The gist of the argument is that experiments can fail for any number of reasons, and so they can't falsify the published result. Null findings should not, in his view, even be published at all. He only gives a cursory nod to the possibility that the initial positive result may be false, then proceeds to ignore it.
This sounds almost bizarre. But here is the unstated assumption that his entire argument rests on: "I already know my idea is right, and the experiment is only there to confirm what I already know." His whole chain of arguments depends on this, and would make no sense without it.
In his view, an experiment is simply there to give evidence for something we already know (or wish) to be true. If it works, that confirms what we already know. A failed replication must thus fail because of experimental error of some kind; since we already know our hypothesis must be true, that's the only inescapable conclusion.
This attitude is the real danger here. If your base assumption is that your failures happen because of experimental error, not because your idea is wrong, then it can become ever so tempting to help an uncooperative experiment along just a bit. Add a few subjects — or remove a couple of "obviously" aberrant data points — to reach statistical significance. Clean up that blurry, messy picture a little. Don't include the failures in your analysis. Make the story clearer and neater. No need to actually run that time-consuming, expensive confirmatory experiment the reviewers wanted. We already know we're right after all.
I bet most cases of falsification and fraud in science started out from this assumption. People came in to the lab knowing they had the right idea, and simply wanted to get the confirmation that will convince everybody else. Telling people — young people just starting out — that this is the right attitude for doing science is dangerous.