Social Relationships and Need-based Justice

Last registered on February 10, 2020


Trial Information

General Information

Social Relationships and Need-based Justice
Initial registration date
November 12, 2019
Last updated
February 10, 2020, 10:35 AM EST



Primary Investigator


Other Primary Investigator(s)

PI Affiliation
University of Vienna
PI Affiliation
University of Vienna

Additional Trial Information

Start date
End date
Secondary IDs
Contemporary research on distributive justice assumes that close social relationships between individuals are critical for the prevalence of the need principle in a group. While recent empirical studies suggest that needs affect how groups distribute available payoffs, the group members’ social relationship has only been implicitly addressed by assuming that group members have sufficiently close relationships with each other for the need principle to appeal. In this study, we examine whether need satisfaction depends on the social relation between the group members in a controlled, laboratory experiment. By means of a group task, we create social proximity among group members. After the group task stage, participants are systematically matched into groups of three where they bargain over the distribution of a joint, exogenously given endowment. The group composition varies with respect to the proximity of social ties. We hypothesize that group members with closer social proximity are more likely to form coalitions and, therefore, are more likely to satisfy each other’s needs. Evidence supporting the theoretical claim that the adherence to the need principle depends on the type of social relationship, contributes to identifying the scope of need-based justice and systemizing the domains of different distributive justice norms.
External Link(s)

Registration Citation

Kittel, Bernhard, Manuel Schwaninger and Réka Szendrö. 2020. "Social Relationships and Need-based Justice." AEA RCT Registry. February 10.
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Experimental Details


Between groups: Groups are systematically matched to vary the social distance between group members according to induced social relations.

Within groups: Artificial need thresholds are varied within constant groups over several rounds.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Need satisfaction rate within groups (NSR-G)
Primary Outcomes (explanation)
We randomly assign need thresholds within groups of three. The need satisfaction rate within groups (NSR-G) measures how many of these need thresholds are satisfied (1, 2, or 3) after a bargaining game. Prior experiments showed that this variable is binary for practical purposes, since virtually all groups satisfy either 2 or all 3 thresholds.

Secondary Outcomes

Secondary Outcomes (end points)
Coalition formation
Secondary Outcomes (explanation)
We induce social relations via a group task in stage 1. The participants bargain in new groups in stage 2. Group decisions in the bargaining game in stage 2 are reached via majority rule. Hence, we can observe which participants form coalitions and whether these have closer or more distant social relations.

Experimental Design

Experimental Design
We conduct an anonymous, computerized laboratory experiment with 3 stages.

In stage 1, we induce close (i.e. relatively closer) social relationships through an incentivized, cooperative task played in groups of three. In the control group participants play a single player version of the same task.

In stage 2, the participants are systematically matched into new groups of three and are able to negotiate (in terms of numbers) in private with the two other players over the distribution of fixed payoffs in an incentivized, unstructured bargaining game. We match according to a between-subject treatment design:
- In the control treatment, groups in stage 2 consist of three participants who played the previous task individually.
- In treatment 1, groups in stage 2 consist of three participants who played the previous task in three different groups.
- In treatment 2, groups in stage 2 consist of three participants of which two played the previous task in the same and one in a different group.
- In treatment 3, groups in stage 2 consist of three participants who played the previous task in the same group.

In stage 3, the participants play a real-effort task. The task is only payoff relevant if the payoff obtained in stage 2 is equal or exceeds an individually assigned threshold (need). We explain the meaning and consequences of the thresholds before stage 2. The assigned thresholds of all group members are common knowledge during stage 2.
Experimental Design Details
The group task in stage 1 follows the ‘Wordfind game’ proposed by Laura A. Dabbish (2008). We conducted a manipulation test of the group task in June 2019. Utilizing the IOS (Aron, 1992) and IIS (Tropp & Wrights, 2001) after the group task, the pretest shows that participants feel significantly closer to individuals who were previously part of the same group than to individuals who were part of a different group (p = 0.01). Likewise, individuals who are matched with new group members feel less close to the new group than individuals who stay in the same group (p = 0.03).

In stage 2 participants bargain over the distribution of 24 payoff points 8 times consecutively. The sum of the assigned thresholds always add up to 15, but each round the inequality of thresholds between the same three participants increases within the treatments. I.e.:
- Round 1: 5 - 5 - 5
- Round 2: 4 - 5 - 6
- Round 3: 3 - 5 - 7
- Round 4: 2 - 5 - 8
- Round 5: 1 - 5 - 9
- Round 6: 0 - 5 - 10
- Round 7: 0 - 3 - 12
- Round 8: 0 - 1 - 14

Round 1 is independent of previous outcomes and, hence, allows an independent, statistically sound comparison between the treatments. Rounds 2 - 8 can be affected by the new thresholds levels, but also by learning, experience (effect of previous bargaining outcomes, e.g. reciprocity), and overarching strategic considerations (e.g., fairness). To minimize the influence of experience and meta-strategies on the bargaining outcomes, we pay only one round, which is randomly selected after the experiment. To minimize the influence of learning on the bargaining outcomes we randomize round 2-8, which in theory should entail the same average learning effects across the different rounds. We argue this ensures the best design given the restriction that we can only conduct a limited number of between-subject treatments due to a limited subject pool.

The real effort task in stage 3 consists of a weighted mix between math puzzles, word finding games and trivia questions. We do not provide information about the difficulty of the tasks, nor the average payoff from the tasks. However, we ask about the expected payoff from the tasks for oneself and others.

We test the following hypotheses:
- Hypothesis 1: NSR-G of treatment 3 is higher than in the control treatment, treatment 1 and 2.
- Hypothesis 2: The higher the inequality of need thresholds, the lower the NSR-G.
- Hypothesis 3a: Within treatment 2, subjects who played together in stage 1 are more likely to form coalitions in stage 2 than subjects who did not.
- Hypothesis 3b: Within treatment 2, subjects who played together in stage 1 are more likely to satisfy their need thresholds in stage 2 than the need thresholds of subjects who did not.
- Hypothesis 4: The more rounds the groups play in stage 2, the less effective are the induced differences of the social relationship in stage 1.
Randomization Method
Randomization done by the program hroot (via a computer algorithm)
Randomization Unit
Students (registered on hroot)
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
360 students
Sample size: planned number of observations
120 groups
Sample size (or number of clusters) by treatment arms
20 groups control, 20 groups treatment 1, 60 groups treatment 2, 20 groups treatment 3
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
n.a. (due to unknown effect sizes) However, since 20 observations on the group level per treatment seem relatively few, we are prepared to conduct further waves. At this stage it is not feasible to conduct more sessions at once, since we challenge the laboratory capacity if we invite more than 360 students in one wave.

Institutional Review Boards (IRBs)

IRB Name
German Association for Experimental Economic Research e.V.
IRB Approval Date
IRB Approval Number


Post Trial Information

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Is the intervention completed?
Data Collection Complete
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Program Files

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