Pics: Fig S1 @ https://science.sciencemag.org/content/sci/suppl/2019/06/19/...
That doesn’t look like any wallet I’ve ever seen. Did it really have to be clear and look like a plastic envelope? Maybe not enough random people would pick it up if it was a real dark wallet (vs say a staff member who cleans the place)?
It’s always good to question how the experiment reflects real life if we’re going to use it to influence real life policy and business decisions. But it’s possible this still sufficiently measured people’s honesty since the basic idea is the same (returning found property of value).
The other factor is the job title. Wouldn’t a “Software Engineer” be less likely to seem in need rather than the average (ie, working class) job title? Given a large enough pool I’m sure this could influence how people factored in the effort of finding the person vs feel-good emotional (or moral, ideological, etc) reward of doing good.
Basically: if the amount of the money mattered, then wouldn’t the job title of this new person whom you only know has business cards and a good job?
The disadvantage of using a clear business-card case over a traditional wallet is clear, in that it is relatively unusual. The advantage of using a clear case, however, is that it affords considerably more experimental control in that you can be relatively certain that every recipient knows what is inside. With a wallet, there will be variation in who decides to inspect the wallet, and that introduces selection effects into the experimental design (i.e., are those who are willing to look inside a wallet, compared to those who don't, different in their degree of honesty?). This makes interpreting the evidence a lot more challenging.
FWIW we examined how our measure of civic honesty compares to other known proxies of honest behavior (tax evasion, corruption, etc) within and between countries. If there was something artificial or unique about our setting -- such as using unusual clear business card cases -- then you wouldn't expect our results to generalize or correlate with other measures of honest behavior. However, we find response rates correlate very highly with these other proxies of honesty, suggesting that they are tapping into some broader construct.
