Roland Fryer, Professor of Economics at Harvard, conducted research on how incentive pay affected teacher and student performance. From the abstract:

Financial incentives for teachers to increase student performance is an increasingly popular education policy around the world. This paper describes a school-based randomized trial in over two-hundred New York City public schools designed to better understand the impact of teacher incentives on student achievement. I find no evidence that teacher incentives increase student performance, attendance, or graduation, nor do I find any evidence that the incentives change student or teacher behavior. If anything, teacher incentives may decrease student achievement, especially in larger schools.

In explaining these results, Fryer considered four possibilities, concluding,

we argue that the most likely explanation is that the NYC incentive scheme, along with all other American pilot initiatives thus far, is too complex and provides teachers with too little agency.

In other words, if people don't see a strong, direct connection between incentive pay and teaching, it won't motivate them to do teach better, and if they don't perceive themselves as in control over what and how they teach, then they won't be motivated to improve their teaching.

That fits in with the Learning and Fun post on Feynman, Daniel Pink's detesting of the question, "What is your passion?", and the perspectives of self-determination and flow (see, for example, Where Does Curiosity Go? and Engagement and Flow).

In short, to improve at one's work (or anything else), people need to feel that they in control of their lives and their work.