https://research-explorer.ista.ac.at 2000-01-01T00:00+00:00 1 monthly https://research-explorer.ista.ac.at/record/19903 Hübner, Valentin 2025 Cooperation, that is, one person paying a cost for another's benefit, is a fundamental principle without which no form of society could exist. The extent to which humans cooperate with each other is also an essential feature that differentiates them from other animals. Cooperation occurs even in the absence of altruistic motivations, when it is selfishly incentivised by the expectation of a future reward. For example, many economic interactions are well described that way. This kind of cooperation requires that people exhibit reciprocal behaviour that acts as a mechanism that rewards cooperation. With game-theoretic models, it is possible to formally study potential such mechanisms and under what conditions they can exist. This thesis contributes to this effort by analysing recently introduced models of cooperation that advance on previous work by taking into account the potential for pre-existing inequality among cooperating individuals as well as the different forms that reciprocity can take. Individuals may differ both intrinsically, in their abilities, as well as extrinsically, in the amount of resources they have available. Allowing for such differences in a model of cooperation helps to understand how inequality affects the potential for, and outcomes of, cooperation among unequals. In this thesis, it is shown that in the presence of intrinsic inequality, a similar unequal distribution of resources can increase the potential for cooperation. This effect is stronger the smaller the group is in which cooperation takes place. It is also shown that under particular assumptions, if the unequal members of a group vary the size of their contributions to a cooperative effort over time, they can thereby increase their efficiency and improve the collective outcome. Cooperative behaviour in a two-person interaction can be rewarded either by direct reciprocation whenever the same two people interact again, or indirectly by a third party who observed the interaction. In the latter case of indirect reciprocity, individuals are proximally rewarded by a good reputation, which ultimately translates to being rewarded with cooperative behaviour by others. This mechanism can enable selfishly motivated cooperation even in circumstances where individuals are unlikely to meet again, akin to how money facilitates trade. While these two forms of reciprocity have mostly been studied in isolation, this thesis analyses both direct and indirect reciprocity in a general model in order to compare their relative effectiveness under different circumstances. The contribution of this thesis is an extension of previous work regarding a specific kind of interaction, whose parameters allow for convenient mathematical analysis, to the most general set of possible interactions. https://research-explorer.ista.ac.at/record/19903 https://research-explorer.ista.ac.at/download/19903/19976 eng Institute of Science and Technology Austria info:eu-repo/semantics/altIdentifier/doi/10.15479/AT-ISTA-19903 info:eu-repo/semantics/altIdentifier/issn/2663-337X https://creativecommons.org/licenses/by-nc/4.0/ info:eu-repo/semantics/openAccess Hübner V. Reciprocity and inequality in social dilemmas. 2025. doi:<a href="https://doi.org/10.15479/AT-ISTA-19903">10.15479/AT-ISTA-19903</a> ddc:519 Reciprocity and inequality in social dilemmas ISTA Thesis info:eu-repo/semantics/doctoralThesis doc-type:doctoralThesis text http://purl.org/coar/resource_type/c_db06 https://research-explorer.ista.ac.at/record/9829 Baranov, Dmitry Šverko, Tara Moot, Taylor Keller, Helena R. Klein, Megan D. Vishnu, E. K. Balazs, Daniel ; https://orcid.org/0000-0001-7597-043X Shulenberger, Katherine E. 2021 In 2020, many in-person scientific events were canceled due to the COVID-19 pandemic, creating a vacuum in networking and knowledge exchange between scientists. To fill this void in scientific communication, a group of early career nanocrystal enthusiasts launched the virtual seminar series, News in Nanocrystals, in the summer of 2020. By the end of the year, the series had attracted over 850 participants from 46 countries. In this Nano Focus, we describe the process of organizing the News in Nanocrystals seminar series; discuss its growth, emphasizing what the organizers have learned in terms of diversity and accessibility; and provide an outlook for the next steps and future opportunities. This summary and analysis of experiences and learned lessons are intended to inform the broader scientific community, especially those who are looking for avenues to continue fostering discussion and scientific engagement virtually, both during the pandemic and after. https://research-explorer.ista.ac.at/record/9829 eng American Chemical Society info:eu-repo/semantics/altIdentifier/doi/10.1021/acsnano.1c03276 info:eu-repo/semantics/altIdentifier/issn/1936-0851 info:eu-repo/semantics/altIdentifier/e-issn/1936-086X info:eu-repo/semantics/altIdentifier/wos/000679406500002 info:eu-repo/semantics/altIdentifier/pmid/34228432 info:eu-repo/semantics/openAccess Baranov D, Šverko T, Moot T, et al. News in Nanocrystals seminar: Self-assembly of early career researchers toward globally accessible nanoscience. <i>ACS Nano</i>. 2021;15(7):10743–10747. doi:<a href="https://doi.org/10.1021/acsnano.1c03276">10.1021/acsnano.1c03276</a> News in Nanocrystals seminar: Self-assembly of early career researchers toward globally accessible nanoscience info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/9402 Schmid, Laura ; https://orcid.org/0000-0002-6978-7329 Chatterjee, Krishnendu ; https://orcid.org/0000-0002-4561-241X Hilbe, Christian ; https://orcid.org/0000-0001-5116-955X Nowak, Martin A. 2021 Direct and indirect reciprocity are key mechanisms for the evolution of cooperation. Direct reciprocity means that individuals use their own experience to decide whether to cooperate with another person. Indirect reciprocity means that they also consider the experiences of others. Although these two mechanisms are intertwined, they are typically studied in isolation. Here, we introduce a mathematical framework that allows us to explore both kinds of reciprocity simultaneously. We show that the well-known ‘generous tit-for-tat’ strategy of direct reciprocity has a natural analogue in indirect reciprocity, which we call ‘generous scoring’. Using an equilibrium analysis, we characterize under which conditions either of the two strategies can maintain cooperation. With simulations, we additionally explore which kind of reciprocity evolves when members of a population engage in social learning to adapt to their environment. Our results draw unexpected connections between direct and indirect reciprocity while highlighting important differences regarding their evolvability. https://research-explorer.ista.ac.at/record/9402 https://research-explorer.ista.ac.at/download/9402/14496 eng Springer Nature info:eu-repo/semantics/altIdentifier/doi/10.1038/s41562-021-01114-8 info:eu-repo/semantics/altIdentifier/e-issn/2397-3374 info:eu-repo/semantics/altIdentifier/wos/000650304000002 info:eu-repo/semantics/altIdentifier/pmid/33986519 info:eu-repo/semantics/openAccess Schmid L, Chatterjee K, Hilbe C, Nowak MA. A unified framework of direct and indirect reciprocity. <i>Nature Human Behaviour</i>. 2021;5(10):1292–1302. doi:<a href="https://doi.org/10.1038/s41562-021-01114-8">10.1038/s41562-021-01114-8</a> ddc:000 A unified framework of direct and indirect reciprocity info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1