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Low-Cost Contact Interventions Can Increase Inter-Ethnic Trust when Previous Contacts Were Scarce: Evidence from Senegal

Last registered on March 04, 2021


Trial Information

General Information

Low-Cost Contact Interventions Can Increase Inter-Ethnic Trust when Previous Contacts Were Scarce: Evidence from Senegal
Initial registration date
March 04, 2021

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 04, 2021, 10:03 AM 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
Universite Alioune Diop de Bambey
PI Affiliation

Additional Trial Information

Start date
End date
Secondary IDs
Existing experimental evidence on the contact hypothesis Allport (1954) has mainly used long and unstructured interventions, with implications for replicability and scalability of existing contact protocols. We here test the effect of brief contacts, using a structured protocol that can be implemented in wide range of situations at a reasonable cost. We also examine the targeting of populations that are more suited to contact interventions based on pre-experimental contact with out-group members. Contact is found to be effective at increasing trust when prior exposure to out-group is low and no effect is found when prior exposure to out-group is high.
External Link(s)

Registration Citation

Clochard, Gwen-Jiro, Guillaume Hollard and Omar Sene. 2021. "Low-Cost Contact Interventions Can Increase Inter-Ethnic Trust when Previous Contacts Were Scarce: Evidence from Senegal." AEA RCT Registry. March 04.
Experimental Details


Short discussion
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Amount sent in a Trust Game and a novel measure of prejudice
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Upon arrival, subjects were assigned to one of three treatments: Contact, Photo or Anonymous.
Experimental Design Details
The Contact treatment resembles the protocol developed by Aron et al. (1997): subjects are paired with an assistant, and take turns in answering a series of questions. The questions, directly drawn from the ``Closeness-Generating Procedure'' in Aron et al. (1997), gradually become more self-disclosing and relationship-building. The first questions are fairly neutral, to get the procedure started (e.g. ``Before making a telephone call, do you ever rehearse what you are going to say? Why?''). The second set of questions then aims to reveal more-personal details (e.g. ``What do you value most in a friendship?'', ``How do you feel about your relationship with your mother?''). Last, the third set covers very personal topics, to create a strong link between the two individuals (e.g. ``If you were going to become a close friend with your partner, please share what would be important for him or her to know''. The subject and the assistant were both asked to answer these questions (without any supervision from experimenters).

In the Photo treatment, subjects are again paired with one of the assistants from the Contact treatment. However, they do not meet them, but are only shown their photo with their names - which include considerable information about ethnicity Mabudike (1976).

In both the Contact and the Photo treatments, subjects were explicitly told that the games played during the experiment will be with the person presented (either in person or in the photo).

In the Anonymous treatment, subjects are not presented the person with whom they will play, and are rather told that they are going to play with ``someone selected at random''.

We decided to select assistants from outside the experimental subject pool - as opposed, for instance, to other subjects - for several reasons. First, because they will meet multiple subjects, we can introduce individual assistant fixed effects in the Contact and Photo treatments. Second, this was one way of ensuring that at least one person in the pair was literate, and therefore did not require a third person to supervise the discussions (which could have influenced the results). Third, we used assistants for feasibility reasons, as we used a paper format for the photos in the Photo treatment and so required photos in advance. Last, having assistants as pairs allowed us to randomize meetings with respect to ethnicity, which would have been much more difficult otherwise, especially in the fishing village which is almost entirely ethnically homogeneous.
Randomization Method
Assignment to treatment by time of arrival (by groups of 3, first enlisted to contact, second to photo, third to anonymous)
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
No clusters, individual treatment
Sample size: planned number of observations
254 individuals
Sample size (or number of clusters) by treatment arms
108 anonymous, 90 contact, 94 photo
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Collection Completion Date
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials