Randomized control trial on anticipation of smart phone habits

Last registered on November 30, 2020


Trial Information

General Information

Randomized control trial on anticipation of smart phone habits
Initial registration date
November 29, 2020

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
November 30, 2020, 11:33 AM EST

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



Primary Investigator


Other Primary Investigator(s)

PI Affiliation
IE University
PI Affiliation
IE University

Additional Trial Information

On going
Start date
End date
Secondary IDs
This research explores whether small monetary incentives are effective in reducing smartphone usage by 30% from subjects' baseline usage. In addition, we investigate whether our intervention leads to lasting behaviour change once the incentives are removed. We also study whether the anticipation of receiving incentives in the future, leads to a pre-emptive reduction of smartphone usage. Finally, the study will provide insights on the effects of reduced smartphone usage on educational performance and psychological outcomes, such as cognitive skills.
External Link(s)

Registration Citation

PHAM QUANG, DUC, JEEVA SOMASUNDARAM and Laura Zimmermann. 2020. "Randomized control trial on anticipation of smart phone habits." AEA RCT Registry. November 30. https://doi.org/10.1257/rct.6826
Sponsors & Partners

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Experimental Details


Small monetary incentives combined with a 30% reduction target.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Daily smartphone screen time
Primary Outcomes (explanation)
The daily smartphone usage over the experimental period elicited via screen time apps.
The smartphone usage data collection will be collected by asking subjects to activate a feature in the iPhone (Screen Time) or Android phone (an app called Screen Time downloadable from the Google Play Store). Subjects will take screenshots of their average weekly screen time usage and submit them via a survey.

Secondary Outcomes

Secondary Outcomes (end points)
Grade Point Average
Cognitive skills
Social network data
Sleep and Physical Activity
Secondary Outcomes (explanation)
GPA data will be collected from the university
Cognitive skills:
- inhibitory functions (Stroop Color-Word Interference Test),
- reasoning (Nonsense Syllogism Test),
- self-reported measures distractibility, procrastination, self-control and smartphone dependence
Social network data (from the screenshots)
Sleep and physical activity will be elicited via screenshots of the iPhone Health app

Experimental Design

Experimental Design
We test monetary incentives that are effective in reducing smartphone usage.
Experimental Design Details
Week 1: baseline screen time data collection

Subjects are randomized into two conditions.

(1) Control condition: No incentives or targets for rest of the experimental period

(2) Anticipation condition:

Treatment period
Week 2 (7 days): Informed about the next period's incentives and target
Week 3-4 (14 days): Incentivized 2 euros everyday the screentime is 30% less than the baseline usage

Week 5-7: no incentives or targets, follow-up screen time data collection

Randomization Method
Ramdomization done in R software.
Randomization Unit
At the individual level, each subject is randomly allocated to control or treatment condition.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
Sample size (or number of clusters) by treatment arms
Control Condition: 34
Treatment Condition: 35
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
IE Research Committee
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials