Controversy over providing financial incentives to research participants has a long history and remains an issue of contention in both current discussions about research ethics and for institutional review bodies/human research ethics committees which are charged with the responsibility of deciding whether such incentives fall within ethical guidelines. The arguments both for and against financial incentives have been well aired in the literature. A point of agreement for many is that inducement in the form of financial incentive is permissible when (...) the risk of harm to the individual is negligible in terms of degree and probability of occurrence. In the absence of harm to the individual, encouraging more people to participate in research would appear to be a good thing in so far as it will lead to statistically more robust research outcomes, which can then be translated into better healthcare and other practice. Whilst, on the face of it, this position seems highly defensible, I will explore the possibility that it is counterproductive – that is, providing individuals with financial incentives to become research participants may have the unintended outcome of reducing participation rates in some areas of research. In exploring this idea I will draw on empirical findings from the literature on crowding-out – the hypothesis that providing monetary incentives to people can backfire by overall reducing intrinsic motivation, in this instance intrinsic motivation to behave altruistically or undertake civic duties. (shrink)