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.

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.

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!