Local competition promotes hurtful behavior towards unknown others

Humans frequently cooperate to achieve benefits unattainable through selfish behavior. Punishment of free-riders is key for sustaining cooperation, but also costly, raising questions about the origins of such behavior. Some evolutionary models suggest that individuals may be willing to hurt unknown others in competitive environments. However, empirical evidence about the effect of the scale of competition on strategies involving hurtful behavior in human groups, such as spite, retaliation for hurting, and punishment of free-riders, is missing. Using a laboratory experiment, we manipulate the scale of competition to investigate its influence on hurtful and helpful behaviors between unknown humans in an indirect reciprocity game. We observe distinct behavioral patterns between local and global competition. When competition is local and thus confined to take place within isolated groups, we find frequent hurting as an expression of spite and retaliation. In contrast, when competition exten..., 156 subjects participated in the experimental sessions that were conducted at the CREED laboratory of the University of Amsterdam. Participation was voluntary, and subjects were recruited through email announcements from a standard university subject pool. Each experimental session lasted approximately 60 minutes. Subjects' total earnings in euros were determined by the relative ranking of the points (denoted by ‘francs’ in the experimental instructions) earned over all the rounds of the indirect reciprocity game. The only difference between the treatments is how the ranking is determined for these euro earnings, either within a local group or globally across several groups. By design, average earnings were 20 euros in both treatments.
Each subject participated in only one session, and none had previously participated in a similar experiment. Subjects were seated in separate cubicles, which ensured anonymity during the experiment. We consider each group of 6 subjects as one independent ..., # Local competition promotes hurtful behavior towards others

\[Access this dataset on Dryad [https://doi.org/10.5061/dryad.mcvdnckd6](https://doi.org/10.5061/dryad.mcvdnckd6)]
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The raw data for the study is in CRSU_rawdata.csv. The variable definitions are shown at the bottom of this README.txt file.
Information for the strategy classification (one row for each of the 156 subjects) is in Strategy_Class.csv. The variable definitions are shown at the bottom of this README.txt file.
Human subjects ethics committee approval included in Ethics_approval_UvA_2019_EC_20190128040115.pdf

## Analysis code:

Data processing and statistical tests use Stata version 19.
Note: The labels period and round are used interchangeably.
Note: Statements to \"drop if round>90\" can be omitted to conduct analysis for all 100 rounds, as reported in section 5 of the Supplemental Online Materials.

1. Table2.do provides the calculations and statistical tests for results shown in Table 2 of the paper. It also calc..., Consent was provided by subjects in accordance with regulations at the University of Amsterdam (reference EC 20190128040115; ethics committee approval included in Dryad files)., Subjects provided consent, including consent to publish de-identified data, in accordance with regulations at the University of Amsterdam.