For that matter, what motivates you? This is an interesting video. (Hat tip to Why Homeschool.) Although the model is from the business world, it certainly could apply to education. True to the research findings, my own kids are not motivated by rewards when there is even a rudimentary cognitive process involved in the work. This research actually gives unschooling (done right) a lot of support.
Wherefore is there a price in the hand of a fool to get wisdom,
seeing he hath no heart to it?