Many of these studies appear to be variations on the form "We selected some people, gave them some money and told them we'd be back to check up on how they were

Many of these studies appear to be variations on the form "We selected some people, gave them some money and told them we'd be back to check up on how they were doing." I wonder if there's a significant effect from the expectation that being part of the study will improve one's life. Perhaps receiving attention from authority figures (PhD or MD), and potentially their judgement, might alter behaviour in similar ways to the "honesty box" experiment [1]. It seems like there might also be some bias in selection - presumably one has to consent (in writing) to be part of a long-term study. Perhaps this encourages participants to think of the future and might influences decision-making away from short-term goals and towards "investment" uses of the money rather than ephemeral ones. I'm looking forward to seeing the results of their differential experiment, and whether there's as much difference between the $333 and $20 groups as there is between the $20 group and the "$0 group" of the general population. [1] http://rsbl.royalsocietypublishing.org/content/2/3/412 http://rsbl.royalsocietypublishing.org/content/2/3/412