The cost of intrinsic motivation - Policy interventions and their effects on behavioral spillovers
Last registered on August 06, 2019


Trial Information
General Information
The cost of intrinsic motivation - Policy interventions and their effects on behavioral spillovers
Initial registration date
August 05, 2019
Last updated
August 06, 2019 11:52 AM EDT
Primary Investigator
ZEW - Leibniz Centre for European Economic Research
Other Primary Investigator(s)
Additional Trial Information
In development
Start date
End date
Secondary IDs
C91, D91, Q50
The experimental design is conceived, in order to investigate how the influence of policy interventions, which target pro-environmental behavior, can lead to different degrees of behavioral spillover effects. We center the analysis on policy measures ranging from liberal paternalism to enforced regulation. Thereby, we exploit a characteristic of these measures; namely, the variations in subjects’ perceived voluntariness to conduct the targeted behavior. The perception of choosing a moral behavior voluntarily leaves room for warm glow and intrinsic motivation, which are assumed to mediate behavioral spillover effects. The experimental analysis will be conducted in a between-subject design with a non-student sample. The experiment consists of two subsequent pro-environmental tasks, for which extrinsic motivation is induced using three different policy interventions, comprising of either nudge, a monetary incentive or enforced compliance. Based on insights from the literature suggesting that the degree of voluntariness is pivotal for the size of behavioral spillover effects, we hypothesize that a larger the degree of perceived voluntariness in the first task, leads to lower effort in the second pro-environmental task.
External Link(s)
Registration Citation
Alt, Marius. 2019. "The cost of intrinsic motivation - Policy interventions and their effects on behavioral spillovers ." AEA RCT Registry. August 06.
Former Citation
Alt, Marius. 2019. "The cost of intrinsic motivation - Policy interventions and their effects on behavioral spillovers ." AEA RCT Registry. August 06.
Experimental Details
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Subjects donations in the second task at the intensive and extensive margin.
Primary Outcomes (explanation)
After answering the discrete choice questions, subjects have the option to donate their show up fee to an environmental NGO.
Secondary Outcomes
Secondary Outcomes (end points)
Time needed to answer comprehension quesitons in the first part. Mistakes made, when answering comprehension questions.
Secondary Outcomes (explanation)
Comprehension questions are asked in order to ensure that subjects have understood the topic of the discrete choice experiment. However, as in four of five treatment, answering the comprehension quesions generate a donation to an afforestation project, it is also conceived as a pro-environmental real effort task.
Experimental Design
Experimental Design
The design aims at isolating the effect of policy interventions to incentivize pro-environmental behavior on subsequent pro-environmental behavior. The experiment is embedded in a discrete choice experiment, in which subjects must answer comprehension quesions in order to proceed to the decision stage. We turn this task in a pro-environmental real effort task, by tellinjg participants that each correctly answered question will lead to the plantation of a tree in an afforestation project. In additional treatments, effort is further incentivized by social comparison, monetary incentives and a punishment scheme. Also, a baseline is added as a control, in which answering the comprehensions questions has no material consequences. After the experiment, subjects have the opportunity to donate the participation fee to an environmental NGO, not being related to climate or afforestation. This represents the second behvavioral spillover task. The difference in donations between the baseline treatment and the respective other treatments will determine the behavioral spillover effect. As we keep the environmental outcome constant in the first task, we are able to isolate the effect of external pressure through policy interventions on behavioral spillover effects in form of subsequent donation levels.
Experimental Design Details
The experimental design is conceived to isolate the effects of policy interventions, implemented to induce pro-environmental behavior, on behavioral spillovers effects. To achieve this, we apply five treatments using a between subject design in an artefactual field experiment. These treatments are listed in Table 1 along with information on the incentive schemes applied, the existence of an environmental context in task 1 and the planned number of observations (relies on power analysis, see Figure 1 in Appendix). Table 1 Treatment Incentive scheme Environmental context of task 1 Observations Baseline No incentive X 100 NoIncentive No incentive ✓ 100 Nudge Environmental impact & social information ✓ 100 Money 0. 5€ / answered question ✓ 100 Force Time punishment for not answering correctly ✓ 100 The experimental design is built around a discrete choice experiment and exploits that participants are asked comprehension questions in order to access the decision stage after having read information on the product of relevance. We construct a real effort task by generating a donation to an afforestation project for each correctly answered comprehension question, in which effort materialized in environmental benefit. This represents the first pro-environmental behavior in the experiment. To further incentivize this pro-environmental behavior task, we introduce a nudge, monetary incentives and a punishment mechanism in different treatments. The second pro-environmental behavior task is given by offering subjects the opportunity to donate parts of their payoff to environmental NGOs, which are not related to afforestation or climate. On the last page, a questionnaire must be filled, containing questions on environmental attitudes or demographic information among others. In the following, the treatments are described in more detail. The ‘baseline’ treatment serves as a control treatment to assess donation behavior in the absence of preceding environmental contributions. In this treatment, subjects are asked to answer the comprehension questions. However, answering correctly has no material consequences, neither for the participants’ payoff, nor in terms of environmental contribution. In the second task, subjects have the option to donate a share of their endowment to three different charities (WWF, NABU, Food Bank Mannheim). The treatment will serve for baseline comparisons, in order to investigate the differences in donations between the baseline treatment and the treatments, in which subjects made an environmental contribution in the first PEB-task. This difference will determine the size of the behavioral spillover effect. The ‘NoIncentive’ treatment is structured in a similar to the ‘baseline’ treatment. The only difference is given by the consequences of answering the comprehension questions in the first task. Here, each exercise, which is solved by subjects, generates a donation to ‘Eden Reforestation Project’, an environmental NGO that has the objective to engage local citizens in developing countries into afforestation projects. Thereby, solving one exercise generates a donation, which suffices to finance the plantation of a tree in the afforestation project. The ‘Nudge’ treatment distinguishes from the ‘NoIncentive’ treatment by the means of motivating subjects to perform the first PEB-task. While there is no specific incentivation in the ‘NoIncentive’ treatment, in the ‘Nudge’ treatment subjects receive information on their relative performance compared to other participants in a real time feedback mode. The real time feedback is applied during the process of answering the comprehension questions. Each round it is signaled to participants via emoticons and a graph whether their performance is within the upper 25 percent, average or lower than average performance cluster of participants who have answered this question before. Hence, this treatment aims to increase subjects’ motivation by raising their ambitions to perform better than others and manipulates the social norm by conveying that providing high effort is the socially appropriate behavior. In the ‘Money’ treatment, solving exercises does not only lead to a contribution to an afforestation project, but also increases subjects payoff by 1€ per question. In order to avoid endowment effects, we assure that each subject is endowed with the same amount of money when taking the donation decision irrelevant of treatment. This is achieved by remunerating subjects in the other treatments for making hypothetical purchase decisions in the discrete choice experiment instead of paying them for each comprehension question. The ‘Punishment’ treatment is set up similarly to the ‘NoIncentive’ treatment, but is framed to make subjects feel pressured to answer the comprehension questions. In addition, we implement a time punishment for not answering correctly. Subjects who have failed to answer a comprehension question correctly must wait 15 seconds to be able to proceed with the experiment and try to answer the question again. The NoIncentive treatment is designed in order to determine the behavioral spillover effect in the absence of any incentivation of the first pro-environmental behavior task. The other three treatments (Nudge, Money, Punishment) are conceived to assess if there are significant differences in behavioral spillover effects compared to the ‘NoIncentive’ treatment. We exploit the different degrees of perceived external pressure to perform the task, which are a characteristic of the policy measures applied in the treatments. The hypotheses comprise of Hypothesis 1, stating that there will be negative behavioral spillover effects, as subjects in the "NoIncentive" treatment will have donated significantly less than subjects in the "baseline" treatment. Also, we assume that the highest external pressure is exerted in the "punishment" treatment, followed by the "Money" treatment and complemented by the "Nudge". The least external pressure is acted upon subjects in the "NoIncentive" treatment. Based on this, it is hypothesized that behavioral spillover effects are crowded out by external pressure of the policy interventions. Therefore, in Hypothesis two, we expect to see the largest donations in "baseline". This is followed by significantly lower donations in the "punishment" treatment and even lower donations in the "money" treatment. The nudge will lower the donatoin level even further and the least donations are expected to be collected in the "NoIncentive" treamtment, based on the external pressure exerted on participants in the treatments respectively.
Randomization Method
By a computer.
Randomization Unit
Assignment to treatments is determined randomly for each subject on an individual level with within-session variation.
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
500 individual observations distributed over five treatments
Sample size: planned number of observations
500 Individuals
Sample size (or number of clusters) by treatment arms
100 observations in "baseline.
100 observations in "NoIncentive".
100 observations in "Nudge".
100 observations in "Money".
100 observations in "Punishment".
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We base our power calculation on the meta-analysis of Blanken et al (2015) on behavioral spillover effects. We average the effect size of 11 studies, most similar to our design, to obtain an idea of the expected effect size. Based on this, the effect size necessary to observe a behavioral spillover effect is given by d=0.42 (Cohen's d). This corresponds to 92 observations per treatment necessary to obtain a power of 80%. For more information, see attached pre-analysis plan. Blanken, I., van de Ven, N., & Zeelenberg, M. (2015). A meta-analytic review of moral licensing. Personality and Social Psychology Bulletin, 41(4), 540-558.
IRB Name
IRB Approval Date
IRB Approval Number
Analysis Plan

There are documents in this trial unavailable to the public. Use the button below to request access to this information.

Request Information
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers