Intrinsic motivation, Fryer was surprised to find, was not affected significantly, and one year after the study's conclusion, 60 percent of the gains made by the sample group had been retained. Incentivized reading, it seemed, worked for certain students. Observing such sustained increases in reading proficiency led Fryer to his most important finding: effort, or “inputs,” could be incentivized, while improved scores, or “outputs,” could not. (Another study conducted by Fryer, released as a working paper last month, found that a combination of similar “input” incentives—involving parents, teachers, and students—yielded even more impressive results.)