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Nudges in "Equilibrium"

Last registered on April 28, 2019

Pre-Trial

Trial Information

General Information

Title
Nudges in "Equilibrium"
RCT ID
AEARCTR-0002435
Initial registration date
December 21, 2017

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
December 22, 2017, 11:02 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
April 28, 2019, 5:49 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Region

Primary Investigator

Affiliation
Hebrew University of Jerusalem

Other Primary Investigator(s)

Additional Trial Information

Status
In development
Start date
2018-01-01
End date
2019-08-31
Secondary IDs
Abstract
"Nudges" have increasingly shown to be cost-effective tools for promoting a wide range of behaviors, from medication adherence to saving to energy efficiency. But most research evaluates one intervention in isolation on target outcomes. As such, we have little understanding of how campaigns might interact with one another, or whether they generate spillovers in unanticipated domains. This paper explores the hypothesis that such campaigns might interfere with one another due to limited attention. I propose a simple framework, motivated by a taxonomy of attention from the psychology literature that distinguishes between “internal” and “external” attention. I test the predictions of the framework using an experiment in which individuals receive combinations of messages and incentives for two healthy behaviors.
External Link(s)

Registration Citation

Citation
Trachtman, Hannah. 2019. "Nudges in "Equilibrium"." AEA RCT Registry. April 28. https://doi.org/10.1257/rct.2435-6.1
Former Citation
Trachtman, Hannah. 2019. "Nudges in "Equilibrium"." AEA RCT Registry. April 28. https://www.socialscienceregistry.org/trials/2435/history/197924
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
There are two interventions that we will implement for two health behaviors in various combinations across treatment arms. The first is a messaging program: subjects will receive two daily messages about the behavior, one that is a simple reminder, and another that contains information about the behavior's benefits. The second is an incentive program: participants will earn one lottery ticket for every day they successfully do the behavior, and winning tickets will be drawn at the end of the treatment period. Both interventions will last 4 weeks.
Intervention (Hidden)
See pre-analysis plan.
Intervention Start Date
2019-01-02
Intervention End Date
2019-02-23

Primary Outcomes

Primary Outcomes (end points)
Whether or not participants engaged in each of the two behaviors, at the individual-day level
Primary Outcomes (explanation)
See pre-analysis plan.

Secondary Outcomes

Secondary Outcomes (end points)
Expectations, opt-outs, response to a surprise raffle via SMS, score on quiz about information sent via messages, health
Secondary Outcomes (explanation)
See pre-analysis plan.

Experimental Design

Experimental Design
Some participants will receive message or incentive programs for only one behavior, and some will receive messaging programs for both behaviors. The key outcome of interest will be whether or not participants engage in each action at the individual-day level. By looking at spillovers and interactions between interventions, we will be able to distinguish between two types of limited attention, internal and external.
Experimental Design Details
See pre-analysis plan.
Randomization Method
Randomization is done in office by a computer with re-randomization (see Pre Analysis Plan)
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
n/a
Sample size: planned number of observations
3780
Sample size (or number of clusters) by treatment arms
Each treatment arm will have a slightly different size, computed in a power calculation that depended on various factors (minimum detectable effect, serial correlation of the outcome, variance of the outcome).
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
The minimum detectable effect size for both spillovers and crowd-out is a 35% reduction in a behavior. This will translate into different units and standardized effects depending on the outcome.
IRB

Institutional Review Boards (IRBs)

IRB Name
Yale Human Subjects Committee
IRB Approval Date
2018-12-17
IRB Approval Number
2000021379
Analysis Plan

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Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
March 31, 2019, 12:00 +00:00
Data Collection Complete
Yes
Data Collection Completion Date
April 30, 2019, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
3818
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
3818
Final Sample Size (or Number of Clusters) by Treatment Arms
811 control, 754 x messages, 794 y messages, 817 x and y messages, 642 y incentives
Data Publication

Data Publication

Is public data available?
Yes

Program Files

Program Files
Yes
Reports, Papers & Other Materials

Relevant Paper(s)

Abstract
Impact evaluations of behavioral interventions typically focus on target outcomes. Might interventions induce negative spillovers on other behaviors? I run a large field experiment in which individuals receive combinations of messages and incentives promoting two healthy behaviors, meditation and meal logging. I find that the interventions reduce completion rates of the opposite behavior by 19-29%. I find that interventions with larger target effects do not necessarily generate larger negative spillovers, and demonstrate implications for cost-effectiveness analysis. I investigate the mechanisms behind the observed spillovers.
Citation
“Does Promoting One Healthy Behavior Detract from Others? Evidence from a Field Experiment” Forthcoming, American Economic Journal: Applied Economics.

Reports & Other Materials