Introduced in Chapter 7, the familiarity loop describes a process by which marketing experts sandwich a new, unknown product between two familiar products. The human brain craves familiarity. One example Duhigg provides is that of butchers attempting to sell organ meat to American consumers during World War II, when consumers could not easily access choice cuts of meat. When these organ meats were churned, encased, and repackaged into something familiar, Americans learned to eat them because they appeared familiar. As Duhigg explains, “Whether selling a new song, a new food, or a new crib, the lesson is the same: If you dress a new something in old habits, it’s easier for the public to accept it” (210). Duhigg’s description of the familiarity loop relates to one of the book’s major themes, which is the skill with which corporations play on human behavior to market consumer goods. The familiarity loop is one tactic among many that marketing experts use to catch the eye of the buyer.

The author introduces the Golden Rule of habit change early in the book: “You Can’t Extinguish a Bad Habit,” he pronounces, “You Can Only Change It” (63). Because habits are so deeply embedded in our basal ganglia, attempting to eliminate them is impractical.