Something like 90 percent of humans ingest caffeine regularly, making it the most widely used psychoactive drug in the world, and the only one we routinely give to children (commonly in the form of soda). Few of us even think of it as a drug, much less our daily use of it as an addiction. It’s so pervasive that it’s easy to overlook the fact that to be caffeinated is not baseline consciousness but, in fact, an altered state. It just happens to be a state that virtually all of us share, rendering it invisible.
– from This Is Your Mind on Plants book by Michael Pollan