Earlier quoted context omitted.
> For healthy adults, the FDA says 400 mg a day is OK. But consuming much more than that can have dangerous, negative effects. And the milligrams add up quickly. A medium-size coffeehouse coffee can contain more than 300 mg, and most 16-ounce energy drinks contain between 160 and 240 mg of caffeine… 3-4 cups might be on the high end of the safe spectrum, depending on what your idea of a "cup" is. (For the record, 3 h…
> (For the record, 3 half-litre beer steins of coffee a day turned out to be a spectacularly bad idea, even if hearing colours was briefly entertaining.) I've consumed caffeine to the point of serious gastric distress and very mild heart palpitations and I've never experienced synesthesia. I'm unwilling to push beyond that to higher doses, but two or three 12-cup pots a day of light roast filtered black coffee is abo…
Perhaps someone can design an (safe) experiment to measure the effect of caffeine in synesthesia ...