### The Brain’s Now

Our perception of time raises all sorts of questions, Eagleman began. “Why does time seem to slow down when you’re scared? And why does it seem to speed up as you get older?”

With an onscreen demonstration, Eagleman showed that “Time is actively constructed by the brain.“ His research has shown that there’s at least a 1/10-of-a-second lag between physical time and our subjective time, and the brain doesn’t guess ahead, _it fills in behind_. “Our perception of an event depends on what happens next.” In whole-body terms, we live a half-second in the past, which means that something which kills you quickly (like a sniper bullet to the head), you’ll never notice.

In order to manage a realistic sense of causality, the brain has to calibrate the rate of different signals coming into it. When that system malfunctions, you can get “credit misattribution”—the sense that “I didn’t do that!” It may explain why some schizophrenics think that their normal internal conversation is voices coming from somewhere else, and it might be curable by training their brain to manage signal lags better.

Is “now” expandable? Why do you seem to experience time in slow motion in a sudden emergency, like an accident? Eagleman’s (terrifying) experiments show that in fact you don’t perceive more densely, the amygdala cuts in and _records the experience_ more densely, so when the brain looks back at that dense record, it thinks that time must have subjectively slowed down, but it didn’t. “Time and memory are inseparable.”

This also explains why time seems to speed up as you age. A child experiences endless novelty, and each summer feels like it lasted forever. But you learn to automatize everything as you age, and novelty is reduced accordingly, apparently speeding time up. All you have to do to feel like you‘re living longer, with a life as rich as a child’s, is to never stop introducing novelty in your life.