Why Default Nudge Works

We ask our respondents about repeated binary choice questions. Our interventions are about "default" options for binary choice questions.

Specifically, we have one control condition in which subjects make binary choice without default nudge, and the following four treatment conditions in which the subjects make binary decisions with the following default nudge:
i) simple default nudge where one alternative is selected as default,
ii) 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,
iii) default nudge with endowment where the default choice is associated with endowment effect, and
iv) default nudge with endorsement where the default choice is associated with endorsement in the question.

With the design, we investigate how much the default nudges increase the propensity to select "favorable" options and what would be the mechanism when default nudge works.

2024-02-05

2024-02-19

Our primary outcome variable for the survey experiment is the choices for the binary choice questions.

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.

Not available

Randomization is done in an office by a computer.

The unit of randomization is at the individual level.

No

1500 individuals for online experiment and 35 individuals for fMRI experiment

1500 individuals for online experiment and 50 for fMRI experiment

For the online survey experiment, we have five different modality of questions, which we regard to be different experiments.
As each subject answer 10 total questions, each subject answers two questions for each modality. We manipulate them with how defaults are set for these binary questions. Since there are five different treatment conditions (including a control condition), each treatment arm for the online survey has (1500x10)/(5x5) = 120.