What Deci found, and then confirmed in two additional studies he conducted shortly thereafter, was almost the opposite. “When money is used as an external reward for some activity, the subjects lose intrinsic interest for the activity,” he wrote.5 Rewards can deliver a short-term boost—just as a jolt of caffeine can keep you cranking for a few more hours. But the effect wears off—and, worse, can reduce a person’s longer-term motivation to continue the project.
