Shank Daniel B, Kashima Yoshihisa, Saber Saam, Gale Thomas, Kirley Michael
Melbourne School of Psychological Sciences, The University of Melbourne, Victoria, Australia.
Department of Computing and Information Systems, The University of Melbourne, Victoria, Australia.
PLoS One. 2015 Mar 23;10(3):e0120379. doi: 10.1371/journal.pone.0120379. eCollection 2015.
Empirical findings on public goods dilemmas indicate an unresolved dilemma: that increasing size-the number of people in the dilemma-sometimes increases, decreases, or does not influence cooperation. We clarify this dilemma by first classifying public goods dilemma properties that specify individual outcomes as individual properties (e.g., Marginal Per Capita Return) and group outcomes as group properties (e.g., public good multiplier), mathematically showing how only one set of properties can remain constant as the dilemma size increases. Underpinning decision-making regarding individual and group properties, we propose that individuals are motivated by both individual and group preferences based on a theory of collective rationality. We use Van Lange's integrated model of social value orientations to operationalize these preferences as an amalgamation of outcomes for self, outcomes for others, and equality of outcomes. Based on this model, we then predict how the public good's benefit and size, combined with controlling individual versus group properties, produce different levels of cooperation in public goods dilemmas. A two (low vs. high benefit) by three (2-person baseline vs. 5-person holding constant individual properties vs. 5-person holding constant group properties) factorial experiment (group n = 99; participant n = 390) confirms our hypotheses. The results indicate that when holding constant group properties, size decreases cooperation. Yet when holding constant individual properties, size increases cooperation when benefit is low and does not affect cooperation when benefit is high. Using agent-based simulations of individual and group preferences vis-à-vis the integrative model, we fit a weighted simulation model to the empirical data. This fitted model is sufficient to reproduce the empirical results, but only when both individual (self-interest) and group (other-interest and equality) preference are included. Our research contributes to understanding how people's motivations and behaviors within public goods dilemmas interact with the properties of the dilemma to lead to collective outcomes.
即增加规模——困境中的人数——有时会增加、减少或不影响合作。我们通过首先将指定个体结果的公共物品困境属性分类为个体属性（例如边际人均回报），将群体结果分类为群体属性（例如公共物品乘数）来澄清这一困境，从数学上表明随着困境规模的增加，只有一组属性可以保持不变。基于集体理性理论，我们提出个体在个体和群体偏好的驱动下进行决策。我们使用范·兰格的社会价值取向综合模型，将这些偏好操作为自我结果、他人结果和结果平等的融合。基于这个模型，我们接着预测公共物品的收益和规模，结合控制个体与群体属性，如何在公共物品困境中产生不同程度的合作。一项二（低收益与高收益）乘三（2人基线组与保持个体属性不变的5人组与保持群体属性不变的5人组）析因实验（群体n = 99；参与者n = 39）证实了我们的假设。结果表明，当保持群体属性不变时，规模会降低合作。然而，当保持个体属性不变时，收益低时规模会增加合作，收益高时则不影响合作。通过基于主体的个体和群体偏好相对于综合模型的模拟，我们将一个加权模拟模型拟合到实证数据上。这个拟合模型足以重现实证结果，但前提是同时包含个体（自利）和群体（他利和平等）偏好。我们的研究有助于理解公共物品困境中人们动机和行为如何与困境属性相互作用从而导致集体结果。
