I'd have to look for that. I'm not aware of such conclusions stated in psychological research, though that may simply be because I didn't get to any of the research papers that included such conclusions. Psychology is, always has been, and likely always will be a fuzzy science. There are too many variables involved to properly control them and get proper conclusions, and too many ethical issues with some of the studies that would be needed to improve upon that. That leads to a series of less-incorrect conclusions and less-misleading theories, so I wouldn't be surprised to find there were some studies that initially supported the idea of rewarding participation. More likely, however, the results were overgeneralized and misapplied in the expression to the general population (the biggest problem with most pop-science articles), leading to unsupported conclusions.What about when the advice was by peer reviewed psychologists and said the same things?