How does choice affect beliefs?

Last registered on June 17, 2020


Trial Information

General Information

How does choice affect beliefs?
Initial registration date
June 17, 2020

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
June 17, 2020, 10:31 AM EDT

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



Primary Investigator

Vienna University of Economics and Business

Other Primary Investigator(s)

PI Affiliation
Central European University

Additional Trial Information

In development
Start date
End date
Secondary IDs
People tend to be optimistic about their own future. For example, compared to rational beliefs,investors typically expect higher returns from their funds. In line with these observations, previous research has documented that owning a product leads to more optimistic beliefs about its value.However, in many important economic contexts, people choose the products for themselves (e.g.they decide to invest in a particular fund). We propose and experimentally test the explanation that, beyond the effect of ownership, making a choice can lead to additional belief distortions. Using a between-subject design, we compare a person who chooses a product to a person who receives the same product exogenously. This comparison controls for the effect of ownership on beliefs. To address the key concern of endogenous choice, we vary the choice set to create predictable variation in choice.
External Link(s)

Registration Citation

Hajdu, Gergely and Balázs Krusper. 2020. "How does choice affect beliefs?." AEA RCT Registry. June 17.
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Experimental Details


The main task of participants is to estimate the payoff probabilities of made-up financial portfolios. The main intervention is that participants either receive one of the portfolios (Allocation condition) or choose one of the portfolios (Choice condition). We inform participants that they will get a reward if the portfolio they own– chosen or received – pays off. Besides the main interventions, we create two additional treatments to study the mechanism. In the Relative Choice condition, participants have to submit their estimates before the choice. In the Ego Choice condition, participants read a short text about the positive relationship between IQ and the quality of financial decision making.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Beliefs about payoff probabilities
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Participants complete four rounds. In each round, they are asked to estimate payoff probabilities of made-up financial portfolios. They receive a signal that helps them to find out the relative ranking of the payoff probabilities while the absolute levels remain uncertain.
Experimental Design Details
Randomization Method
Randomization is done by the computer. First, individuals are assigned to one of the treatment groups. Second, in each round, one of the portfolios is randomly selected for individuals in the Allocation condition.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
1000 individuals.
Sample size: planned number of observations
8000 individual-portfolio pairs..
Sample size (or number of clusters) by treatment arms
350 individuals Allocation, 350 individuals Choice, 150 individuals Relative Choice, 150 individuals Ego Choice.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
CEU Econmics Doctoral Committee
IRB Approval Date
IRB Approval Number
Analysis Plan

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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