Reciprocity: Warm glow or guilt aversion?

Last registered on January 27, 2021


Trial Information

General Information

Reciprocity: Warm glow or guilt aversion?
Initial registration date
November 30, 2020
Last updated
January 27, 2021, 8:11 AM EST



Primary Investigator

University of Innsbruck

Other Primary Investigator(s)

PI Affiliation
Victoria University of Wellington

Additional Trial Information

On going
Start date
End date
Secondary IDs
We utilize the trust game to investigate in an online experiment whether trustees (receivers) who send money back are rather motivated by positive feelings such as warm glow or by avoiding negative feelings such as guilt. In the trust game itself, distinguishing between altruism and guilt aversion is senseless as both higher levels of altruism and higher levels of guilt aversion motivate the receiver to return higher amounts. However, distinguishing between the two kinds of motivations is important when receivers can opt out from the trust game. Specifically, we have developed a behavioral game theoretic model that yields the following main result: If reciprocal behavior is motivated by guilt aversion (warm glow), then those who return higher amounts have a higher (lower) incentive to opt out. Distinguishing between warm glow and guilt aversion is hence important to understand if and why subjects who self-select or who are randomly assigned to situations where trust matters behave more or less trustworthy. A pilot with 200 subjects suggests that reciprocity seems to be motivated by positive emotions (warm glow) rather than by avoiding negative emotions (guilt).
External Link(s)

Registration Citation

Feess, Eberhard and Florian Kerzenmacher. 2021. "Reciprocity: Warm glow or guilt aversion?." AEA RCT Registry. January 27.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Our primary outcome is whether subjects in the role of trustees decide to participate in a trust game.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The experiment will be conducted online and participants will be recruited using Amazon Mechanical Turk.
Subjects will be randomly assigned to groups of two. The two group members are randomly assigned the roles of trustor (sender) and trustee (receiver).
In addition to the participation fee, trustors receive $0.50. They have to decide whether they want to keep this amount or send it to the trustee. If they decide to give it to the trustee, the amount is tripled and the trustee receives $1.50. The trustee can then decide how much money to send back to the trustor (between $0 and $1.50).
The amount the trustee wants to send back will be elicited according to the strategy method assuming that the trustor has sent the money. After trustees make their decision, they will be given an exit option. If they decide to not play the trust game, they receive a certain payment of $0.50 in addition to their participation fee. In this case, trustors simply keep their additional $0.50.
Following this baseline setting, we plan to conduct another treatment in which trustees are informed about the frequency of trustors sending the money in the previous treatment in order to fix beliefs.
Experimental Design Details
Randomization Method
Participants will be randomly assigned to groups and roles (computerized).
Randomization Unit
Individual level randomization.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
No clusters.
Sample size: planned number of observations
We plan to collect 880 observations, i.e. 880 participants.
Sample size (or number of clusters) by treatment arms
We plan to collect 440 observations in the baseline treatment and 440 observations in the other treatment.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
In a pilot experiment with 200 participants (100 trustees), a logit regression revealed a positive impact of the amount trustees intend to give to trustors on their participation decision (p=0.279, including controls about the beliefs on the behavior of trustees, gender, age, and risk attitude). The probability of the mean amount sent back participating was at 65% and the probability of the mean plus one standard deviation amount sent back participating was at 72%. Assuming this effect prevails, a logit regression power analysis reveals that we need about 220 observations of trustees (one-tailed test, 5% significance level, 80% power). UPDATE: Adjustment of sample size: We have collected 220 observations for trustees in each of the two treatments. In line with our pilot, the impact of the returned amount on the participation decision is always positive, both with non-parametric and parametric analyses. However, depending on the combination of control variables, the amount is sometimes significantly positive at the 5%-level and sometimes barely insignificant at the 10% level, so that no robust conclusions can be drawn yet. We therefore decided to increase the statistical power by doubling the number of observations to see whether results prevail.

Institutional Review Boards (IRBs)

IRB Name
Board for Ethical Questions in Science of the University of Innsbruck
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