Experimental Design
Subjects in our online survey experiment (main study) respond to 10 binary choice questions. The contexts of binary choice questions are the ones used in extant default nudge studies, such as whether to participate in activities related to environmental conservation, join a pension plan, or donate to charitable causes. There are five types of question modalities, and our respondents answer two for each modality, resulting in 10 total questions.
For each of the five modalities, the subjects are randomly assigned to one of the following:
1) Control where there is no default nudge,
2) simple default nudge in which one alternative is selected as default,
3) default nudge with ease where the questions are asked with many words so that the subject will find it easy to choose the default choice,
4) default nudge with endowment where the default choice is associated with endowment effect, and
5) default nudge with endorsement where the default choice is associated with endorsement in the question.
Patterns (3) - (5) are prepared to investigate potential mechanism why default nudge may work, that is the effect of ease, that of persuasion, and that of endowment, respectively.
In our analysis, after summarizing the descriptive statistics of the experiment, we regress the choices in each question onto the dummy variables for treatments (2) to (5) with and without different types of controls.
For fMRI experiment, each subject answers 50 questions, that is treatments (1) to (5) for two questions for each 5 modalities. For fMRI experiment, analysis using fMRI images will be conducted.