Using the word "manipulate" might carry too heavy a negative connotation than you might be used to ascribing to rewards, but if you strip the connotations from

Using the word "manipulate" might carry too heavy a negative connotation than you might be used to ascribing to rewards, but if you strip the connotations from the word, it's clear that rewards expressly manipulate others. "Do this and I'll give you that" is explicitly a way of affecting others' actions by providing external motivation. It is an attempt to control others behaviors (this is meant plainly, not necessarily judging whether trying to exercise such control is bad). The intention behind the reward might not even be to control, but unfortunately that doesn't change that that it does do control even if inadvertently. Yes, according to Alfie Kohn, such rewards, even innocent seeming things like praise, can indeed backfire. Marshall Rosenberg had this question: When someone does something that you want them to do, what reason would you like for them doing that thing? Would you like them to do it purely due to the reward (or fear of the withdrawal of the reward, which is functionally a punishment)? Or would you like them to do it because they themselves see the value in it and are self-motivated? This is not to say that rewards have no place in life, just that they are a tool that should be carefully considered, and to understand that they will not solve most problems and may make things worse sometimes. The alternative to rewarding or punishing others involves working with them in a less coercive fashion. But that's hard, and I don't know that there's a ready answer for what exactly to do in each situation. NVC could help sometimes.