Ernst Cramer, the late, great editor-in-chief of the German daily Die Welt, once recounted how as a college student in America in the midwest, just after World War II, he questioned in a math class whether the textbook was not mistaken in a particular instance. The lecturer reflexively, and rather sternly, dismissed the possibility. Several months later, Cramer was working on a farm during summer vacation when he looked up to see his professor jogging across the field from a parked car in the distance. “Cramer,” a repentant voice yelled, “you were right – the book was wrong and they’ve changed that section!”

Cramer related the tale as an endearing anecdote from his early experience in America. We’re similarly charmed by the graciousness and integrity of Cramer’s math professor. But we’re re-telling the story here because the professor’s first response reveals two failings all too common in managers. One is the reflex always to bestow uncritical faith in authorities (including one’s own superiors) and handed-down rules; the other, the quick dismissal of seemingly irreverent assertions.

We all have such blind spots, and they are weaknesses we should combat. Even that idea is unfashionable in an era when we are urged to focus on polishing strengths. In the world of professional music, it’s often the opposite. Most conductors, for instance, begin rehearsals by directing the orchestra immediately to the most difficult passages in a given piece, and spend most time on them, because they are areas of weakness.

But how do managers work actively to fight weaknesses of which, by definition, they are insufficiently aware? We’ll offer a few tactics we have used deliberately to counter the effects of three infamous cognitive biases.

To fight confirmation bias, have a devil’s advocate.

Confirmation bias refers to our tendency, when receiving new information, to process it in a way that it fits our pre-existing narrative about a situation or problem. Simply put, if you’re already inclined to believe that the French are rude, you will find the examples on your trip to Paris to validate your thesis. Disconfirming evidence – the friendly waiter, the helpful bellman – gets pushed aside. They’re just “the exception.” Warren Buffett says, “What the human being is best at doing, is interpreting all new information so that their prior conclusions remain intact.” He knows he is prone to it himself.

Attorneys, debaters, and politicians engage in a kind of confirmation bias when, in order to make a case, they select certain data while deliberately neglecting or deemphasizing other data. But confirmation bias can cause disaster in business and policy when it leads a decision-maker to jump to conclusions, fall prey to misguided analogies, or simply exclude information that inconveniently disturbs a desired plan of action.

What to do? The only remedy is to make sure you have a full and accurate picture available when making important decisions. When you have a theory about someone or something, test it. When you smell a contradiction – a thorny issue, an inconsistency or problem – go after it. Like the orchestral conductor, isolate it, drill deeper. When someone says – or you yourself intuit – “that’s just an exception,” be sure it’s just that. Thoroughly examine the claim.

Dealing with confirmation bias is about reining in your impulses and challenging your own assumptions. It’s difficult to stick to it day in and out. That’s why it’s important to have in your circle of advisers a brainy, tough-as-nails devil’s advocate who – perhaps annoyingly, but valuably – checks you constantly.