I would guess what GP is referring to is something along the lines of this book: https://www.danpink.com/books/drive/ https://www.danpink.com/books/drive/ IIRC

I would guess what GP is referring to is something along the lines of this book: https://www.danpink.com/books/drive/ https://www.danpink.com/books/drive/ IIRC, the idea is just that money only goes so far up Maslow's Hierarchy of Needs. Once our material well-being is taken care of, we want mastery and autonomy and incentives geared that way are more effective than money.