I counted them. Spent 6 months documenting every thought as it arose on index cards. Literally. I have a couple thousand of them I still have to finish scanning one of these days.
Sometimes i would need four cards at once.
I could time the coming and going of a thought or impression.
It’s about 6 seconds total: about 2 seconds coming in, strong for 4 seconds, and fades within 2 seconds unless I reinforce it.
When multiple thoughts overlap, their timings do too and it takes juggling reinforcing some or compressing them into a single image or word to carry a “lesser” thought to a later point in time 12-16 seconds later so I can unravel it and get it down.
Lots of fun. Had index card piles everywhere and pens so I could capture everything.
I did it from April to Sept 2013 with the bulk of them from May-July and I started to taper off after that.
By that point, I discovered Vine (in July) which was ALSO 6.3 seconds long… the PERFECT time and meshed with my own subjective findings.
So, I can say without doubt: “Now” = 6 seconds.