Not entirely sure why, but out of the meditation techniques I know, Zazen seems to have the biggest positive effect on reaction speed.
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All meditation seems to improve reflexes (I say "seems to" because I can't remember any research), but with Zazen the entire reaction is extremely fast.
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I'd speculate this has something to do with executive function. Executive function obviously includes a lot of reflex inhibition.
With zazen, you specifically avoid engaging executive function to the highest extent possible.
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So when, like now, I'm doing at least an hour of that a day, I find the conscious mind spends a lot of time going "Oh. That happened."
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