Every pilot learns to cross-check instruments rather than trust a single reading — because any one gauge can lie convincingly. The same principle applies when you're scaling a business or trying to lose weight: we almost always rely on one signal (revenue, the scale, how tired we feel) and mistake that single reading for the full picture. The psychologist Paul Meehl spent decades showing that simple checklists of multiple data points consistently outperform expert intuition built on a dominant single cue — not because intuition is worthless, but because it latches onto the most vivid signal and ignores the quieter ones. Today, pick one area where you've been trusting a single metric, and ask what the second or third instrument would actually say.

What is the one number you check most often in your work or health routine — and what would you discover if you deliberately ignored it for a week and measured something else instead?

Drawing from Philosophy of science / Actuarial judgment research — Paul Meehl