under the social bonus? Following Osterloh and Frey (2000) among others, one may assume that rewarding effort in the social-related task may have undermined the intrinsic motivation of FAs and exacerbate free-riding.<sup>20</sup> Because the effort of each FA working in a team is unobservable to other team members, and social outcomes are less reflective of FA effort, Soc-FAs who were offered the social bonus could have experienced, on average, a significant decline in intrinsic motivation and this decline could have exacerbated free-riding in teams. In contrast, the credit bonus may not have affected negatively the intrinsic motivation nor teamwork among Cr-FAs.

In the following subsection we provide evidence of the claim that the social bonus may undermine the intrinsic motivation of Soc-FAs.

# 6.2 Intrinsic motivation and teamwork

Columns 1-3 of Table 7 present three different measures of intrinsic motivation. In the baseline and follow up surveys, FAs were asked to list the things that they liked most about working with NRSP. Column 1 thus reports a dummy variable that equals one if the FA mentioned the ability to help people as what they like most about NRSP. According to this measure, Soc-FAs are 23.4 percentage points less likely to be intrinsically motivated in the follow up survey, compared to control FAs. This decline in intrinsic motivation due to the introduction of the social bonus is statistically significant (p-value is 0.022). In contrast, the decline in intrinsic motivation for Cr-FAs is small (almost half in magnitude), and not statistically significant at conventional levels.

In the follow up survey, FAs were also asked whether they identified with NRSP’s mission and whether they found their work with NRSP satisfying and important. The impacts of bonus on these two alternative measures are presented in Columns 2 and 3, respectively. Soc-FAs are 15.2 and 13.6 percentage points less likely to report being intrinsically motivated compared to control FAs on these two additional measures. The estimates are however not statistically significant at conventional levels, although they are large in magnitude and both indicate a 35 percent decline in intrinsic motivation compared to the control means. In contrast, the impacts on Cr-FAs are negligible and not statistically significant. The standard errors are again large and thus we cannot reject that the impacts of the bonuses in Columns 1-3 are different from each other.

In Column 4, we construct a motivation index by taking an equally weighted mean of the three dummy variables in Columns 1-3. Based on this index, the social bonus decreased intrinsic motivation by 16.7 percentage points (p-value is 0.074). In contrast, the impact of the credit bonus is close

> 20More formally, one may assume that a motivated individual can exert effort e2 = <u>e</u> > 0 at no cost, that is, C(0, e) = 0. Individuals are motivated so long as they are not offered a social bonus. Under a social bonus, the individual is no longer motivated and facing a disutility cost of effort C<sup> ̃</sup> (e1, e2) such that C<sup> ̃</sup> (0, e) > 0. We assume that C12 and C<sup> ̃</sup> cs have the same sign.

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