The “goal” was the same for both sets of customers: Buy eight additional car washes, get a reward. But the psychology was different: In one case, you’re 20 percent of the way toward a goal, and in the other case, you’re starting from scratch. A few months later, only 19 percent of the eight-stamp customers had earned a free wash, versus 34 percent of the head-start group. (And the head-start group earned the free wash faster.) People find it more motivating to be partly finished with a longer journey than to be at the starting gate of a shorter one.
