Is that the example from Freakonomics? I don't remember. Anyway, let's not jump to conclusions so quickly. The fine may not have gotten rid of the guilt. They may have also lost favor for the day care. There could be other explanations.
I honestly can't remember where I first read it- it's been ages since I read freakonomics. A draft of the study can be found [url=citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.37.1417&rep=rep1&type=pdf]here[/url], though (thank you, google scholar). Here's a chunk where they put it much better than I did:
They've done a bunch of other stuff on motivational theory and incentives, including a series of experiments in which 'altruistic' and 'paid' volunteers were asked to answer a series of IQ test questions 'for science'. The unpaid volunteers outperformed the paid ones, although within the 'paid' group, the better-paid ones performed better than the lowly-paid ones. (study is here)
The idea is that it's better to pay nothing than to pay too little. Here's a chunk from their discussion:
Another good example probably the comparison
Richard Titmuss made between British and American blood donation systems in the 1960's. He found that while donation in England and Wales, where all donors are unpaid, increased sufficiently to meet the increased demand for blood products. On the other hand, in the US there was a growth in commercial blood banking and a concomitant fall in altruistic donation, with the rise in commercial supplies insufficient to cope with the fall in unpaid donation. I don't know if that's even true any more, and even if it is, it's only an incomplete explanation- Australia's blood supply is awful, and we rely on unpaid donors. But still.
Did the actual number of donated kidneys go up (adjusted for population and other factors)? Did the proportion of altruistically donated kidneys go down? I guess it's far-fetched to say not. It does mean that people became less willing to give them away, but that's kind of a weird wording. There's been no actual research on motivations.
Yeah, I phrased that stupidly. To clarify: according to Iranian transplant authorities, the actual number of altruistically donated kidneys have gone down, and there's plenty of anecdotal evidence to suggest that asking for a kidney from a relative has become seen as something 'stingy' to do. A small handful of single-centre studies in (mostly not peer-reviewed) journals suggest that the number has remained static, and just the proportion has gone down. A couple of bioethicists associated with the AEI/ CATO institute have said the same thing, but without referencing anything that backs up the numbers they give.
No, I think it's all hilarious. I love SMBC, because it knows the limitations of all of these fields, and makes fun of them all.
I just think "you'll want to use what are called 'fractions'" is the perfect punch line.