The effect of a pen pal program on child outcomes: Evidence from a randomized controlled trial in China

Last registered on March 30, 2023


Trial Information

General Information

The effect of a pen pal program on child outcomes: Evidence from a randomized controlled trial in China
Initial registration date
March 29, 2023

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
March 30, 2023, 4:02 PM EDT

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


Primary Investigator

Institute for Economic and Social Research, Jinan University

Other Primary Investigator(s)

PI Affiliation
University of Chicago
PI Affiliation
Insitute for Economic and Social Research, Jinan University

Additional Trial Information

On going
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Our aim is to study the effect of pen pal programs on child development. We conduct a randomized controlled trail on students in grade 7 (first-year middle school students) in China, in collaboration with the BlueLetter, an NGO specialized in organizing pen pal programs for many years. The program matches each student in the treatment group with a pen pal volunteer, and allow them to communicate by mail for one and half years anonymously and under the supervision of BlueLetter. We plan to (1) examine the causal effect of pen pals on a range of development outcomes, including test scores, cognitive skills, and noncognitive skills (Big Five personlity factors) as well as economic preferences, both immediately after the program ended and longer term effects; (2) study heterogeneous effects for different subgroups. In particular, we will focus on left behind children whose parents were away from home for work in cities. Left behind students are especially likely to suffer from emotional issues, thus could potentially benefit from pen pal programs which provides emotional support; (3) analyze the underlying mechanisms through which the program impacts children. We have collected extensive information regarding the children, their parents and schools before the intervention, and will do so after the RCT. Meanwhile, we will analyze the text contents of the letters exchanged between the student and pen pal volunteers.
External Link(s)

Registration Citation

Feng, Shuaizhang, Yujie Han and James Heckman. 2023. "The effect of a pen pal program on child outcomes: Evidence from a randomized controlled trial in China." AEA RCT Registry. March 30.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Academic achievement measured by test score of Chinese, math, and English. Cognitive skills measured by IQ. Noncognitive skills measured by the Big Five personality traits. Economic preferences measured by time preference, risk preference, and altruism.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We sample all 9 middle schools in Mianzhu county of Sichuan province in China, each of which includes 4-14 classes in grade 7. In the grade 7 of each school, we randomly assign half of the classes in each school into either the treatment or control group. As a result, there are 33 and 31 classes in the treatment group and control group, respectively. For all students in the treated classes, we match them with a pen pal volunteer with whom to have mail correspondence for about one and half years.
Experimental Design Details
Randomization Method
random sampling of classes using stata program on a computer.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
64 classes
Sample size: planned number of observations
1952 students
Sample size (or number of clusters) by treatment arms
33 treated classes and 31 controlled classes
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Institutional Review Board of Social Sciences and Humanities, Jinan University
IRB Approval Date
IRB Approval Number
IRB No. A2009/001-002


Post Trial Information

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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