Brucks Désirée, Marshall-Pescini Sarah, Essler Jennifer L, McGetrick Jim, Huber Ludwig, Range Friederike
Comparative Cognition Unit, Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna, University of Vienna Vienna, Austria.
Front Psychol. 2017 Feb 28;8:270. doi: 10.3389/fpsyg.2017.00270. eCollection 2017.
Cooperation is only beneficial if the outcome is equally shared between individuals involved in the cooperative interaction. A mechanism to limit the development of unequal cooperation is inequity aversion, the negative reaction to unequal treatment. While inequity aversion has been studied extensively across many animal species, it remains unclear whether inequity aversion elicited in experimental settings is directed to the cooperative partner animal or rather to the experimenter distributing the rewards unequally. In the current study we aimed to further investigate whether the presence of an experimenter distributing rewards is essential in order to elicit inequity aversion in dogs. We tested 22 dog dyads in an inequity task, requiring dyads to alternately press a buzzer in order to receive rewards of equal or unequal value. We manipulated the extent of the experimenter's involvement in the task: in the experimenter-present version an experimenter gave a command to the dogs to press the buzzer and delivered the rewards by pushing the bowls into the dogs' enclosure. In contrast, in the experimenter-absent version, no experimenter was visible and the buzzer and bowls were moved from behind a curtain. We found that dogs did not respond to the unequal treatment regardless of the experimenter's involvement in the task. Nonetheless, we found that dogs based their behavior on frustration and social facilitation in the experimenter-absent version of the task, suggesting that a social interaction with an experimenter may be one aspect necessary to elicit inequity aversion. One potential explanation for the absence of inequity aversion in the experimenter-present version of the task might be the reward delivery method. Using separate sets of reward bowls for each dog instead of a shared bowl could have removed a potentially important competitive aspect (i.e., shared resource) from the inequity paradigm. In addition, delivering the rewards via bowls, rather than directly handing the rewards to the dogs, might have caused dogs to perceive the task as less cooperative. These results suggest that both the presence of an experimenter causing inequity and the inclusion of a competitive or cooperative element in the task may be basic requirements for eliciting inequity aversion.
只有当合作成果在参与合作互动的个体之间得到平等分享时，合作才是有益的。一种限制不平等合作发展的机制是公平厌恶，即对不平等对待的负面反应。虽然公平厌恶已经在许多动物物种中得到了广泛研究，但尚不清楚在实验环境中引发的公平厌恶是针对合作伙伴动物，还是针对不平等分配奖励的实验者。在当前的研究中，我们旨在进一步调查实验者分配奖励的存在是否是在狗身上引发公平厌恶的必要条件。我们在一个公平任务中测试了22对狗，要求狗对交替按下蜂鸣器以获得价值相等或不等的奖励。我们操纵了实验者参与任务的程度：在有实验者在场的版本中，实验者向狗发出按下蜂鸣器的指令，并通过将碗推到狗的围栏中来发放奖励。相比之下，在没有实验者在场的版本中，看不到实验者，蜂鸣器和碗从窗帘后面移动。我们发现，无论实验者是否参与任务，狗都不会对不平等对待做出反应。尽管如此，我们发现狗在没有实验者在场的任务版本中，其行为基于挫折感和社会促进作用，这表明与实验者的社会互动可能是引发公平厌恶的一个必要方面。在有实验者在场的任务版本中没有出现公平厌恶的一个潜在解释可能是奖励发放方式。为每只狗使用单独的奖励碗而不是共享碗，可能消除了公平范式中一个潜在的重要竞争方面（即共享资源）。此外，通过碗发放奖励，而不是直接将奖励递给狗，可能导致狗将任务视为不那么具有合作性。这些结果表明，造成不平等的实验者的存在以及任务中包含竞争或合作元素可能是引发公平厌恶的基本要求。
