I found the study "When money doesn't pay" study interesting that the performance paid between $4 and $40 was the same, however, when there was a substantial increase to $400 that people performed worse based on the hierarchy of needs if they have food, water, and shelter. Besides, performance did a person's drive increase? Also was there a point of diminishing returns in relation to desire as the pay increases? With most jobs as the pay increases, so does the responsibility How would those factors factor in?
For the motivation and skill solicitation questions, the "How do you best communicate?" would be a good question because it would allow that person to easily use the Platinum Rule by allowing that person to be treated the way that person would like to be treated.
I also like the "Do you believe that people are born with an innate intelligence or that they can improve it?" I like this question because depending how they answer it could tell you if they have a fixed or growth mentality.