What used to be thought of as the “reptilian core” of our brains—let's now simply speak of those neural circuits governing behavior that seems reflexive, like flinching at a loud noise—should not be underestimated where the harvesting of attention is concerned; for once you recognize the triggers, you begin to see them everywhere: the flashing signs employed by vendors, those bouncing icons on your computer screen, the little pictures of cats or sexy women attached to Internet links. All of these stimuli set off neural responses that cause us to engage, whether we mean to or not. Flipping through a book of classic posters is instructive, for it is almost a catalogue of attention triggers. Motion, color, critters of every kind, sexualized men and women, babies and monsters seem to work best on us. It was the achievement of the late nineteenth century's poster pioneers to recognize these responses and put them to profitable use—a lesson that neither advertisers nor their eventual imitators in government would ever forget.

Tim Wu, The Attention Merchants, loc. 66