Back to History Current Version

Effect of a short term contact intervention on inter-ethnic trust in Senegal

Last registered on February 24, 2022


Trial Information

General Information

Effect of a short term contact intervention on inter-ethnic trust in Senegal
Initial registration date
February 24, 2022

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
February 24, 2022, 1:53 PM EST

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



Primary Investigator

Institute of Social and Economic Research - Osaka University

Other Primary Investigator(s)

PI Affiliation
CREST - Ecole polytechnique - CNRS
PI Affiliation
University Alioune Diop in Bambey

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
We are conducting a lab-in-the-field experiment in Senegal to test the effects of a brief contact on inter-ethnic trust.
External Link(s)

Registration Citation

Clochard, Gwen-Jiro, Guillaume Hollard and Omar Sene. 2022. "Effect of a short term contact intervention on inter-ethnic trust in Senegal." AEA RCT Registry. February 24.
Experimental Details


Short-term contact, adapted from Aron et al. (1997)'s "fast-friend" procedure.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Trust game + measure of prejudice towards the entire outgroup
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Measures of declared trust one month after the experiment
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
See Pre-Analysis Plan
Experimental Design Details
Randomization Method
Randomly assigned based on order of arrival (1 to treatment 1, 2 to treatment 2, 3 to treatment 1, etc...)
Randomization Unit
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
150 per treatment
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Institut Louis Bachelier IRB (IRB00013336)
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents


MD5: 1d031bc79e6ccd2d0ae45b97a8614879

SHA1: 9d97b02d79d2cd2caff67b60abe5bf3733ef696f

Uploaded At: February 24, 2022


Post Trial Information

Study Withdrawal

There is information in this trial unavailable to the public. Use the button below to request access.

Request Information


Is the intervention completed?
Intervention Completion Date
April 29, 2022, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
April 29, 2022, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
895 subjects
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Same: 895 subjects
Final Sample Size (or Number of Clusters) by Treatment Arms
254 control, 300 photo, 341 contact
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

The contact hypothesis posits that interacting with outgroup members can reduce prejudice and improve intergroup relations. While the overall effects of contact have been found to be positive, some studies have found null or even negative effects. We aim to contribute to the understanding of the determinants of contact interventions, by unbundling the bundle represented by contact interventions and testing for the effects of a common component of all existing contact interventions, namely bilateral discussions. We take advantage of the controlled environment of lab-in-the-field experiments and implement a ``fast-friends'' intervention, which aims to create interpersonal closeness quickly, and can be implemented in a wide variety of situations. We run our experiment with a diverse sample from northern Senegal. Our intervention is found to be effective in increasing interethnic trust toward the specific individuals the individual meets. However, we find a backlash effect at the collective level, with contact increasing interethnic prejudice. We analyze the heterogeneity of treatment effects with respect to a predetermined dimension - previous contacts - and using machine learning techniques for dimension selection to avoid overfitting. We find no evidence of heterogeneity in either individual-level trust or outgroup prejudice.
Clochard, G.-J., G. Hollard, and O. Sene (2023). Bringing contact interventions to the lab: Effects of bilateral discussions on interethnic trust in senegal. CREST Working Paper

Reports & Other Materials