Experimental Design Details
Before the actual experiment, participants will answer a questionnaire in which we gather information on trait reactance, environmental preferences, and political orientation (Stage 1). There will be no obvious link between questionnaire and decision experiment. Both stages are separated by a non-trivial amount of time, so that the probability that participants presume a connection is minimized.
The actual experiment consists of ten experimental groups, including a control group (Stage 2). Treatments consist of different ways to affect contributions, introduced by differently characterized sources.
The experiment has a fractional factorial 3x4 design. There are two factors, called source type (ST), and intervention type (IT). ST has three levels (no source (NoS), knowledgeable source (KNO), political source (POL)). IT has four levels (no intervention (NoI), recommendation (REC), default (DEF), restriction (RES)). Two possible combinations of both factors are excluded from the design, i.e. no intervention combined with a knowledgeable, as well as political actor. This results in ten combinations, i.e. experimental groups. The combination of no source and no intervention is referred to as the control group.
Among others, our aim is to test whether participants respond differently to treatments given their respective baseline contributions. Since these would normally be counterfactuals, thusly not observable, we elicit baseline contributions before allocating subjects to treatments. Since, theoretically, eliciting baseline contributions might compromise treatment effects, we test this prior to the actual experiment (Stage 2 Block1): We will conduct two treatments, each in two different versions, prior to the others. With this, we test whether letting participants decide about their contribution two times, i.e. first, uninfluenced (baseline), second, in their respective treatment group, changes contributions in the second round significantly compared to only one (treated) decision. In the two-round design, participants are informed that only one of their decisions will be picked randomly to be realized.
We will do this both for the control group, as well as for the combination of default and knowledgeable actor (DEF-KNO). If contributions in the respective two-round vs. one-round alternatives significantly differ, we will conduct all remaining treatments with only one round. Should there be no significant differences, we will conduct all other treatments with two rounds.