Far too often unwelcome information is tossed aside in favor of the answer we're seeking. That's no surprise, really. But in an age of ubiquitous information, when failures are fast and cheap, it's the discordant data, outliers and paradoxes that can be more informative.
The experiment would then be carefully repeated. Sometimes, the weird blip would disappear, in which case the problem was solved. But the weirdness usually remained, an anomaly that wouldn’t go away.
This is when things get interesting. According to [University of Toronto Psychology Professor Kevin] Dunbar, even after scientists had generated their 'error' multiple times — it was a consistent inconsistency — they might fail to follow it up. 'Given the amount of unexpected data in science, it’s just not feasible to pursue everything.' Dunbar says. 'People have to pick and choose what’s interesting and what’s not, but they often choose badly.' And so the result was tossed aside, filed in a quickly forgotten notebook. The scientists had discovered a new fact, but they called it a failure.
The reason we’re so resistant to anomalous information — the real reason researchers automatically assume that every unexpected result is a stupid mistake — is rooted in the way the human brain works. Over the past few decades, psychologists have dismantled the myth of objectivity. The fact is, we carefully edit our reality, searching for evidence that confirms what we already believe. Although we pretend we’re empiricists — our views dictated by nothing but the facts — we’re actually blinkered, especially when it comes to information that contradicts our theories. The problem with science, then, isn’t that most experiments fail — it’s that most failures are ignored.
Wikipedia: Philosophy of Science