I would like to supplement everyone's excellent answers by saying that sometimes, especially in social science experiments, the choice of incentive is very important. Importantly, the choice of funding source has also been explored somewhat in research methodology literature.
An influential paper in this regard is linked here (paywall) and here (free!) A brief summary of this paper is that, it takes 3 popular incentive choices (in social science for experiments) and looks at the choice of said incentive versus data collection and sampling. These incentives are cash, gift certificate via snail mail and gift certificate via email. The results indicate the cash might be the most effective incentive structure in similar experiments.
In response to a comment, I would state that does exist a relationship between the funding source and incentive choice. In one of our previous projects, where the funding came from a "named" foundation, we had a condition to use funding for participant recruitment in a very specific way.
Disclaimer: The first author is my previous adviser.