Public primary school students were given the chance to deposit money weekly into a lockbox, and they were informed that their accumulated savings would be returned to them at a school-supplies fair at the beginning of the next trimester. Schools were randomly assigned to one of three groups. In the first group, students were offered a “hard” commitment: Their accumulated savings would be returned in the form of a voucher that had to be spent on school supplies. In the second group, students got a “soft” commitment: Their savings would be returned in cash, and could be spent as they wished. The third group of schools continued as normal, serving as a comparison group whose savings and spending money were also observed.

You might think that the “hard” commitment would be the best strategy, since it forces the money to be spent on school supplies. But surprisingly, as we report in a working paper, the soft commitment worked better. Students who got their savings back in cash saved more, and when the program was combined with parental involvement (which was also randomized), the students also bought more school supplies and achieved higher test scores.

The second study took place in Zambia. One problem there, as in other low-income countries, is how to recruit the “right” kind of workers for jobs like teachers and health workers — where “right” refers to those who are capable and genuinely interested in helping the community, not just looking for money and a steppingstone to another job. There is often resistance to increasing what these jobs pay, or otherwise improving their benefits, for fear of attracting opportunists.

The researchers Nava Ashraf and Scott Lee from Harvard Business School and Oriana Bandiera from the London School of Economics and Political Science tested this conventional wisdom by varying whether one particular job benefit — opportunities for career advancement — was advertised in a government recruitment drive for a nationwide health-worker program. The researchers randomly assigned some rural communities to receive advertisements for the jobs that announced opportunities for career advancement, whereas in other areas, the advertisements were silent on this issue.

Contrary to expectation, the researchers reported in a working paper released last year, those recruited with “career” advertisements were more qualified and scored higher on exams during training, and also exhibited the same degree of emphasis on community service. The “go-getters” also outperformed the “do-gooders” on the job, seeing the same number of patients in their health clinics while conducting 29 percent more home visits and twice as many community health meetings. (After being recruited, everyone was told about the opportunities for career advancement, so that no differences in performance could be attributed to differing incentives.)