believe that the spectator choices in the present study reveal moral obligations of importance for understanding human behavior and cooperation in society.

In the experiment, the spectators decide how much to redistribute between two individuals who have earned money by completing an assignment, but where one of them has been unlucky and lost his or her earnings. Our main interest is in how the amount transferred to the unlucky worker depends on whether the two individuals have been part of a system of cooperation or have worked independently. In particular, do spectators consider cooperation to create a special relationship between the two individuals, justifying more redistribution of earnings than when they have worked independently?

The experiment was implemented by combining two infrastructures for data collection. We recruited 1015 individuals to act as spectators through the data-collection agency (TNS Gallup), where the sample is representative of the US population (18+ years old) on observable characteristics (gender, age and geography).<sup>1</sup> At the same time, we recruited individuals or “workers” from an online marketplace for work (Amazon Mechanical Turk) to complete a code recognition task.

The workers received a participation fee of 2 USD and were told that they could earn an extra 6 USD if they completed an assignment. However, they were also told that some of them would randomly lose their earnings and that there would be a distribution phase where a spectator could decide to transfer earnings from a randomly selected worker who had not lost the earnings to an unlucky worker, and thereby determine what the two of them would actually be paid for the assignment. We constructed sets of six workers, where each set was randomly divided into two groups of three workers, group A and group B. A set of six workers constituted a distributive situation for which a unique spectator made a redistributive decision.<sup>2</sup> The workers were placed into one of two conditions in terms of production: independent work or cooperation. If they worked independently, a worker succeeded in doing the assignment and earned 6 USD if he or she completed the task. If they cooperated, a worker succeeded and earned 6 USD only if the two other workers in his or her group also completed the task. Thus, in the cooperation condition, an individual who completed his or her task earned nothing if one of the other two workers did not complete the task. This experimental design captures a key aspect of cooperation as a mutually beneficial activity (Bowles and Gintis, 2011): the success of each individual causally depends on the contribution of other individuals. The workers in both conditions were not told of the existence of other sets of workers or conditions of production apart for their own. All workers were anonymous and could not communicate with each other, which excludes social comparison concerns for the spectators.

In the distributive situations presented to the spectators, all six workers had succeeded in completing the assignment, and, as a result each had earned 6 USD.<sup>3</sup> However, one of the workers, randomly drawn, had lost his or her earnings from the assignment. The task of the spectator was to decide the amount of money, if any, to transfer to the unlucky worker from one of the other five workers in the set. Thus, each spectator made a choice with real economic consequences for others, a fact that was highlighted in the instructions. The spectator’s decision did not affect the payment to the four other workers in the distributive situation, who all received their earnings of 6 USD.

In a 2x2 between-subjects design, which is summarized in Table 1, we varied two aspects of the distributive situation presented to the spectators: first, whether workers had cooperated within

> 1In the appendix, we provide and overview of the background characteristics for the sample in Table A1 and a copy of the instructions given to the spectators in section A.2.

> 2We had six workers in each distributive situation to ensure that the randomly selected worker in each treatment was randomly selected from a pool of workers who had not lost their earnings and to avoid varying the number of workers in the distributive situation across treatments.

> 3We recruited workers until we had 1015 sets of six workers who all succeeded in completing the assignment. Sets of workers in which someone did not complete the assignment were not presented to the spectators in the experiment. The payments to these workers were determined by a spectators recruited separately from the spectators used in the present study, and, therefore, in line with the pre-analysis plan posted on the AEA RCT Registry, their decisions are not included in the present analysis.

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