WE LIKE FEELING CERTAIN

Star Trek’s Spock is overconfident, meaning that his confidence that he’s right outstrips his actual accuracy. In that respect, Spock isn’t all that different from most of us (except that he makes a much bigger deal about how his predictions are objective and “logical,” which is why I’ve chosen to make an example of him). We very often speak as if there’s no chance we could be mistaken—“There’s no way he can make that shot from that distance!” or “I’ll definitely have that done by Friday”—and yet we turn out to be wrong nonetheless. This tendency is known as the overconfidence effect, a well-documented cognitive bias in which people are more confident in their judgments and abilities than is objectively warranted. That gap matters when others rely on a prediction or when a confident judgment discourages further checking.

To be fair, the certainty we express is partly just for simplicity’s sake. Conversation would be unwieldy if we had to stop and assign a probability to every statement we made. But even when someone does prompt us to stop and reflect on our level of confidence, we often claim to be completely certain. You’ll notice this if you search online for phrases like, “How certain are you that” or “How confident are you that.” Here are a few examples I pulled from discussions on Quora, Yahoo! Answers, Reddit, and other forums:

• As a percentage, how certain are you that intelligent life exists outside of Earth? “I am 100% certain there’s other intelligent life.”
• How confident are you that you are going to hit your 2017 sales goals? “I’m 100% confident.”
• Atheists, how confident are you that you won’t convert to a religion like Christianity on your deathbed? “100% confident.”

Everyday life is filled with similar displays of misplaced certainty. Consider Jarred, who insisted he knew every street in the city and didn’t need a GPS, only to get lost three times and turn a one-hour drive into a two-hour ordeal. Or the consultant Elisabeth, who during a meeting announced in an unequivocal voice that a certain company was still expected to earn over $50 million a week. Fifteen highly trained, intelligent people nodded along without question—until news reports later revealed the real figure was closer to $2 to 2.5 million per week. Why did nobody push back? Her expression and tone signaled certainty, and the group accepted the figure without checking it. Confidence made the assertion persuasive; it did not make the estimate reliable.

Even professionals are frequently certain and wrong in their area of expertise. Studies have found that doctors routinely overestimate their ability to diagnose patients. One study examined the autopsy results for patients who had been given diagnoses with “complete certainty,” and found that in 40 percent of those cases, the diagnosis was incorrect. Expertise does not guarantee calibration. In finance, medicine, and project planning, an unjustifiably confident prediction can discourage checks that would expose a costly mistake.

Not all overconfidence is due to motivated reasoning. Sometimes we simply don’t realize how complicated a topic is, so we overestimate how easy it is to get the right answer. A desire to feel certain can also contribute. Certainty is comfortable and can make us feel competent, so we may stop questioning an answer too soon.

So how can you protect yourself from this bias, both in others and in your own thinking? Pause and ask yourself where the information behind your judgment comes from. Was it drawn from reliable, objective sources, or did it emerge from a fleeting impression and an overly self-assured hunch? If the foundation of your certainty is shaky, take time to re-evaluate your conclusions and seek out better data. Developing the habit of questioning even the most confidently spoken statements—while still respecting the speaker—helps bring decision-making closer to reality.

Your strength as a scout is in your ability to resist that temptation, to push past your initial judgment, and to think in shades of gray instead of black and white. To distinguish the feeling of “95% sure” from “75% sure” from “55% sure.” Track predictions made at different confidence levels and compare them with their outcomes. That gives you a way to test whether your certainty matches your accuracy.