Payment for research participation: a coercive offer?

Payment for research participation has raised ethical concerns, especially with respect to its potential for coercion. We argue that characterising payment for research participation as coercive is misguided, because offers of benefit cannot constitute coercion. In this article we analyse the concept of coercion, refute mistaken conceptions of coercion and explain why the offer of payment for research participation is never coercive but in some cases may produce undue inducement.