Abstract This study estimated the effect of receiving help during a disaster on an individual’s subsequent cooperation for a common-pool resource. Such a chain of altruism is called generalized exchange and upstream indirect reciprocity in exchange and cooperation theories. Theoretical studies have pointed out its importance in understanding human cooperation in society. Some researchers on disaster have observed the phenomenon called “disaster area relay”, where disaster victims, having received help during the disaster they experienced, in turn, help victims of another subsequent disaster. However, there are few empirical and systematic analyses of this in actual societal events due to the causal problem. This paper attempted to overcome this problem through a quasi-experimental approach using big data. This paper focused on mutual cooperation through “Free Tank”, which is a common-pool resource in the online community called “mineo-KINGDOM”. The result of difference-in-differences estimation showed that receiving help during a disaster had a positive causal impact on subsequent cooperation for a common-pool resource and reciprocity norm. This result provides assurance that helping has a potential ripple effect on individuals’ cooperation.

本研究は，インターネット上の匿名コミュニティにおいて，いかにして協力的な集団が形成可能かという問いにアプローチするため，いわゆる格安スマホサービスmineo（マイネオ）の提供する「フリータンク」という，顧客同士が協力しあうことで通信パケット量を公共財化するサービスに着目する．最初に，顧客のフリータンクへの通信パケットの提供および引き出し双方の行動履歴データの分析を通して，通信パケットの提供と引き出しの分布に潜む規則性を見い出す．次に，その分布は顧客のどのような行動パターンにより生み出されているのかという疑問に対する説明をシミュレーション実験によって試みる．最後に，ごく一部のユーザによる余剰パケットの一部またはすべての提供によってフリータンクが維持されていることを示す． In this study, to approach the question of how a cooperative group can be formed in an anonymous community on the Internet, we focus on the service that customers can convert their packets into public goods by cooperating with each other, which is called “Free Tank” provided by the mineo, one of the low-cost cell phone service providers. Firstly, through the analysis of the behavior history data of customers regarding both the provision and withdrawal of packets to the Free Tank, we find the regularity hidden in the distribution of the provision and withdrawal of packets. Secondly, we try to explain the question of what kind of behavior patterns of customers creates such distribution by simulation experiments. Finally, this study shows that the Free Tank is maintained by some or all provision of surplus packets of a small number of customers.

type:Departmental Bulletin Paper [要旨]人間社会は昔から様々な形の社会的ジレンマに直面してきたが，現代社会においてはそこに参加する人数が増大している。本研究は，従来の社会的ジレンマ研究における知見が大規模化した社会的ジレンマに適用可能であるかを，現実社会に存在する社会的ジレンマのビッグデータを解析することで検討した。具体的には，日本の仮想移動体通信事業者であるオプテージが提供する「フリータンク」というシステムに着目した。フリータンクの分析の結果，規模が大きくなることで互恵的協力者が減少したことが明らかになった。また，協力を必要とする人がいることへの気づきが，協力行動を促進した。一方で，協力を募ることは，協力行動を促進する効果を持たなかった。[Abstract] Although human societies have faced various social dilemmas throughout history, the number of participants has become so large in modern societies. This study investigated whether the research findings on social dilemmas can be applied to largescale social dilemmas by analyzing big data on social dilemmas. Specifically, we focused on the "Free Tank" system developed by Optage, one of Japan's mobile virtual network operators. The analysis of Free Tank data revealed that the proportion of reciprocal cooperators decreased as the scale of the system increased. Additionally, the awareness of the need for cooperation increased cooperation. Conversely, solicitation for cooperation did not encourage cooperation.

The accumulation of findings that most responders in the ultimatum game reject unfair offers provides evidence that humans are driven by social preferences such as preferences for fairness and prosociality. On the other hand, if and how the proposer’s behavior is affected by social preferences remains unelucidated. We addressed this question for the first time by manipulating the knowledge that the proposer had about the responder’s belief concerning the intentionality of the proposer. In a new game called the “ultimatum game with ambiguous intentions of the proposer (UGAMB),” we made the intentionality of the proposer ambiguous to the recipient. We expected and found that the proposer would make more unfair offers in this new game than in the standard ultimatum game. This expectation can be derived from either the preference-based model or the strategy model of the proposer’s giving decision. The additional finding that more unfair giving in the UGAMB was not mediated by the proposer’s expectation that the recipient would be more willing to accept unfair offers provided support for the preference-based model. Using a psychological measure of cognitive control, the preference-based model received additional support through a conceptual replication of the previous finding that cognitive control of intuitive drive for prosociality in the dictator game, rather than mind reading in the ultimatum game, is responsible for the difference in giving between the two games.

How cooperation is possible has been one of the major puzzles in social sciences. Traditionally, two mechanisms have been proposed to explain cooperation. Cooperation in repeated dyadic interactions has been explained by direct reciprocity, while cooperation between more than two individuals has been explained by indirect reciprocity. Although reputation is theoretically unnecessary to achieve mutual cooperation in repeated dyadic interactions, several experimental studies indicated that people do make use of reputation even in such situations. Therefore, we conducted two experiments to investigate why people make use of reputation in dyadic interactions. Our results revealed that people use reputation because they assume that reputation enables them to predict their partners’ future behaviors in dyadic interactions. We conclude that there is a need to reexamine the system of mechanisms posited to explain the problem of cooperation in particular by expanding the scope of indirect reciprocity.

One of the most well-known models to characterize cooperation among unrelated individuals is Social dilemma (SD). However there is no consensus about how to solve the SD by itself. Since SDs are often embedded in other social interactions, including indirect reciprocity games (IR), human can coordinate their behaviors across multiple games. Such coordination is called linkage'. Recently linkage has been considered as a promising solution to resolve SDs, since excluding SD defectors (i.e. those who defected in SD) from indirectly reciprocal relationships functions as a costless sanction. A previous study performed mathematical modeling and revealed that a linkage strategy, which cooperates in SD and engages in the Standing strategy in IR based on the recipients' behaviors in both SD and IR, was an ESS against a non-linkage strategy which defects in SD and engages in the Standing strategy in IR based on recipients' behaviors only in IR (Panchanathan and Boyd, 2004). In order to investigate the robustness of the linkage strategy, we devised a non-linkage strategy, which cooperates in SD but does not link two games. First, we conducted a mathematical analysis and demonstrated that the linkage strategy was not an ESS against cooperating non-linkage strategy. Second, we conducted a series of agent-based computer simulations to examine how the strategies perform in situations in which various types of errors can occur. Our results showed that the linkage strategy was an ESS only when there are implementation errors in SD. However, the equilibrium of the linkage strategy was unstable when there are perception errors. Since we know that humans are not free from perception errors in their social life, future studies will need to show how perception errors can be overcome in order to provide support for the conclusion that linkage is a plausible solution to SDs. (C) 2016 Elsevier Ltd. All rights reserved.

Although social solidarity is an essential component that helps maintaining social order, what produces solidarity and how does it work have not been fully investigated. We conducted an experiment to examine whether experiencing different forms of social exchange produces different levels of solidarity. We compared four forms of social exchange: reciprocal exchange (exchange resources without negotiation), negotiated exchange (with negotiation), pure-generalized exchange (giver can choose who to give) and chaingeneralized exchange (giver cannot choose who to give). Two dimensions classify these exchanges: the number of players (two vs. more than two), and involvement of negotiation. Reciprocal and negotiated exchanges occur within dyads, while pure- and chain-generalized exchanges involve three or more players. Only the negotiated exchange involves negotiation process the other exchanges are purely unilateral giving. Participants played a one-shot social dilemma game (SDG) before and after social exchange session. The more the players cooperated in SDG, the stronger the social solidarity. Results show that the cooperation rate in SDG increased more in the reciprocal, pure- and chain-generalized exchange conditions than that in the negotiated exchange condition, suggesting that social solidarity is facilitated by experiencing social exchange which does not involve negotiation.

本研究プロジェクトでは性感染症の知識増進を進めるためのフィールド実験を実施することを目指している。2018年度は、その第一歩として、予備調査を行う年度である。そのため、性感染症に関する知識を大学生がどの程度有しているかを確認するためのアンケート調査を設計・実施した。設計は18年度前期に行った。アンケートの内容としては、回答者の性別、性感染症に関する知識を問う質問、リスク態度に関する質問などである。質問内容が性感染症ということで、回答に関してはプライバシーが守られること、回答したくない場合には白紙のまま提出してもかまわないことを徹底した。 アンケート調査の実施校は大阪学院大学(分担者の長塚が担当)、関西大学(代表の小川および分担者の本西が担当）である。回答者はそれぞれの大学の学部生である。具体的には大阪学院大学は主に経済学部生、関西大学は経済学部生と、本学経済実験センターで実施している経済実験の参加者であった。実施時期は2018年10月から2019年3月で、有効回答数としておよそ300名のデータが集まった。18年度中にデータ入力をほぼ完了し、分析に入るところまで進んだ。 同時に性感染症の行動経済学的分析に関する内外の文献調査を実施し、関連する研究の整理を行った(代表の小川および分担者の川村・稲葉が担当)。整理の結果は予備調査にも反映されているだけでなく、今後実施される介入実験の設計にも資するものと考えられる。