I assumed Deja Vu was my brain remembering something I had forgotten. It turns out my brain was doing something far more ordinary and far more useful. It was recognising a pattern.
A neuroscientist named Akira O'Connor at the University of St Andrews has spent years on this. The way he describes it, one part of your brain spots the shape of something familiar and lights up. The fact-checking part then goes hunting for the actual memory behind that feeling, comes back with nothing, and raises its hand to say the pattern is a false one. That small flicker of unease in the middle of deja vu is your brain catching its own pattern matching in the act of being wrong. The people with the sharpest memory systems tend to get it the most.
I have been turning that over lately, because pattern matching is the whole job. Spending years on a factory floor, your mind stops reading every problem from scratch and starts matching it to one you have already solved. That speed is what experience is for. It also has a failure mode, and that is deja vu in a meeting room, the confident sense that you have seen this exact thing before and already know how it ends, when your brain has matched a pattern that was never really there.
Serendipity runs on the very same machinery. The word was invented in 1754 by Horace Walpole, who borrowed it from an old Persian tale about three princes who kept stumbling onto fortune through a mix of accident and close observation. The accident could happen to anyone. The pattern buried inside it shows itself only to the person paying enough attention to catch the odd detail and follow it. The discovery was a pattern all along. It simply arrived dressed as a coincidence.
So I am left holding one idea that has changed how I work. My experience hands me patterns all day long, and the real skill is knowing which ones have earned my trust. The patterns that make me feel instantly certain, the ones that tell me I have already seen this, are usually the ones I need to slow down and question. And the strange little signals I would normally hurry past are often the ones worth following.
I am still learning which of my patterns to trust, and I have come to think that this single skill is most of what we actually mean by judgement.