Many environmental problems represent social dilemma situations where individually rational behaviour leads to collectively suboptimal outcomes. Communication has been found to alleviate the dilemma and stimulate cooperation in these situations. Yet, the knowledge of the basic elements, i.e. the types of information that need to be provided and exchanged to make communication effective, is still incomplete. Previous research relies on ex post methods, i.e. after conducting an experiment researchers analyse what information was shared during the communication phase. By nature, this ex post categorization is endogenous. In this study, we identify the basic elements of effective communication ex ante and evaluate their impact in a more controlled way. Based on the findings of previous studies, we identify four cooperation-enhancing elements of communication: (i) problem awareness, (ii) identification of strategies, (iii) agreement, and (iv) ratification. In a laboratory experiment with 560 participants, we implement interventions representing these components and contrast the resulting levels of cooperation with the outcomes under free (unstructured) or no communication. We find that the intervention facilitating agreement on a common strategy (combination of (ii) and (iii)) is particularly powerful in boosting cooperation. And if this is combined with interventions promoting problem awareness and ratification, similar cooperation levels as in settings with free-form communication can be reached. Our results are relevant not only from an analytical perspective, but also provide insights for social dilemma situations in which effective communication processes cannot be successfully self-organized, calling for some form of external, structured facilitation or moderation.

许多环境问题代表了社会困境，其中个人的理性行为导致集体的次优结果。在这些情况下，人们发现交流可以缓解这种困境并促进合作。然而，基本要素的知识，即需要提供和交换以使沟通有效的信息类型，仍然是不完整的。先前的研究依赖于事后方法，即进行实验后，研究人员分析了在交流阶段共享的信息。本质上，这种事后分类是内生的。在这项研究中，我们确定了事前有效沟通的基本要素，并以更加可控的方式评估了它们的影响。根据以前的研究结果，我们确定了沟通中四个促进合作的要素：（i）问题意识，（ii）战略确定，（iii）协议和（iv）批准。在有560名参与者的实验室实验中，我们实施了代表这些组成部分的干预措施，并在自由（无结构）或无交流的情况下，将合作的结果水平与结果进行了对比。我们发现，促进就一项共同战略达成共识（（ii）和（iii）的结合）的干预措施在促进合作方面特别有力。并且，如果将其与促进问题意识和批准的干预措施相结合，则可以达到与自由形式交流环境中类似的合作水平。我们的研究结果不仅从分析的角度来看是相关的，而且还为无法有效自组织有效沟通过程的社会困境提供了见解，需要某种形式的外部，结构化的促进或节制。