Or autonomy: tell participants they need to design their own coin-flipping experiment, then perform, measure, and report the results. They still might be underp

Or autonomy: tell participants they need to design their own coin-flipping experiment, then perform, measure, and report the results. They still might be underpaid on a $/time basis, but with a greater investment in the process I suspect they'd have a certain amount of pride in ensuring accurate results.