I don’t have hard data, but I think this optimal value is very closely approximated by coffee drinkers’ daily average. 400 ml is about 1.75 cups, and i think the normal distribution of coffee cups among drinkers is centered at ~2 cups. Makes me wonder if we’re all self medicating and accidentally finding the sweet spot.
OR it could be that we find the sweet spot because it's the spot we feel the best.
Well, that's the hardest data of all!
Hmm to feel a bit elevated makes sense. I also have that with one glass of alcohol at certain times. Heart rate goes up, things get a bit more intense. It's a nice vibe if you're open to it. It's also a bit subtle.
For me what I've noticed: 2 cups hits the spot, but I always tend to drink more, around 4 cups. On the 3rd cup my mind gets jittery. It's not so much my body or anything and I don't experience the jitters strongly but at the same time I feel a stronger focus while noticing that stronger focus isn't getting anything extra done. Hence I call it mind jitters.
But I can imagine that at 2 cups people are genuinely just a bit elevated in certain ways.