The Internet, a plain whose grasses hide so many digital predators, can activate that same response in contemporary humans. It offers “fight” and “flight” in one tidy package. Reading emails or hunching over a screen, Stone says, can cause people to go into a kind of resting state. Some 80 percent of people, she has shown, stop breathing (temporarily) or start breathing shallowly (continuously) when they check their email or look at a screen. Stone calls this condition “email apnea.” And she attributes it to our anticipation that the stuff we’re scanning will eventually require a response from us. Our drone-like surveys of our screens will eventually reveal an email from our boss or a note from a friend. And, when that happens, we’ll need to spring to action to respond.