In quantitative finance, your data sampling method changes what you see. Choose the wrong interval and real patterns disappear. I've been thinking lately about how the same problem applies to memory and how I reflect on my experiences.

Calendar bars. The default sampling scheme for a life is calendar bars. Birthdays, new year's, decades, school years. They fire on schedule regardless of whether anything meaningful happened, which means transformative years are equivalent to years with relatively little change. The grid is even, but life experience isn't.

Novelty bars. Memory seems to encode novelty bars. First apartment, first loss, that one semester. Ages 15 to 30 is a period of high novelty: new independence, new relationships, first experiences of basically everything. Your twenties feel like they lasted a decade because your brain was firing a bar often. Your late thirties feel like a weekend because of large intervals between novel experiences.

Depth bars. The 100th weeknight dinner with family contains nominal novelty, which means memory essentially skips it. These are depth bars, periods where nothing new is happening but something is latently accumulating. Skill, familiarity, intuition, identity. They're invisible to the sampling scheme memory uses, but they're foundational in ways novelty bars never are.

Emergence bars. Then there's a fourth type. A bar that fires when the cumulative deviation from expected behavior crosses a threshold. Nothing, nothing, nothing, and then a structural break: emergence bars. No single day of showing up at a job resembles the expertise that eventually materializes. No single conversation in a relationship resembles the closeness that eventually exists. Expertise is emergent, not accumulated, and so the bar only fires in retrospect. When you try to locate it in memory you can't, because the moment of crossing wasn't a moment at all. It was a slow accumulation that only became apparent after the fact.

My reflection on life is written almost entirely in novelty bars, because those are the ones memory encodes. But the actual construction happened in depth bars and emergence bars that I can barely remember at all. The periods I skip over when reflecting are the ones that wrote it.