I seem to recall that the usual result of studies that investigate whether research participants perform better when incentivized is negative. My best guess as to why that would be the case is that people are already surprisingly strongly motivated to do what the researcher wants them to do (remember the Milgram experiment!) I don’t remember seeing any studies specifically of how incentives affect general knowledge tests; of course they could be different from other tasks researchers assign to people, but it would surprise me if that were the case.
I seem to recall that the usual result of studies that investigate whether research participants perform better when incentivized is negative. My best guess as to why that would be the case is that people are already surprisingly strongly motivated to do what the researcher wants them to do (remember the Milgram experiment!) I don’t remember seeing any studies specifically of how incentives affect general knowledge tests; of course they could be different from other tasks researchers assign to people, but it would surprise me if that were the case.