The effect of light on behavioral effects in the lab

Last registered on July 26, 2022


Trial Information

General Information

The effect of light on behavioral effects in the lab
Initial registration date
July 21, 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
July 26, 2022, 1:32 PM EDT

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



Primary Investigator

Texas A&M University

Other Primary Investigator(s)

PI Affiliation
Texas A&M University

Additional Trial Information

On going
Start date
End date
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
Light affects levels of serotonin. Ample evidence has explored the effect of light on eating behavior. Previous literature has also revealed that levels of serotonin affect preferences for fairness (Crockett 2008). More broadly, serotonin can affect mood, sleep, and other health measures (Young 2007) as well as the types of food consumed (Blundell et al 1995). A recently conducted pilot reveals that a student population reveals stronger preferences for fairness in the light than in the dark. In this study, we confirm the findings of this pilot study, varying the amount of light in the room while exploring the classical games where preferences for fairness may be detected and evaluating the payment schemes. We also explore the effects both in a student population and a non-student, general adult population.
External Link(s)

Registration Citation

Palma, Marco and Natalia Valdez Gonzalez. 2022. "The effect of light on behavioral effects in the lab." AEA RCT Registry. July 26.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
We are interested in measuring fairness and cooperation under light exposure
Primary Outcomes (explanation)
We are going to evaluate the responses in the ultimatum game (both amount sent and whether offers are accepted) under the different lighting conditions to evaluate preferences for fairness. We are going to evaluate the responses in the trust game (amount sent and amount returned) under the different lighting conditions. Additionally, we are going to evaluate the contributions to repeated rounds of the public goods game to evaluate cooperation.

Secondary Outcomes

Secondary Outcomes (end points)
We are going to conduct sub-sample analyses and additional tasks to account for the heterogeneity of our sample. If possible, we may include biometric information.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We are going to invite participants to our lab. We will have them exposed to the lighting condition (under 50 lux in the "darkened" condition and at least 800 lux in the "light" condition) before the study starts for a few minutes. We will ensure that there are the appropriate number of participants in the lab for the games that are being played (minimum of 4). They will complete at least one round of two games and multiple rounds of a third game, followed by some additional tasks and demographic questions. Everyone will go through the same order of stages in the experiment. Payment will be handled in economic units in the games that can be exchanged for cash.
Experimental Design Details
Randomization Method
Randomization will be done by flipping a coin.
Randomization Unit
Randomization will be done at the session level.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
According to power calculations from our pilot study, we need approximately 40 observations per cell
Sample size: planned number of observations
We will need to recruit about 160 students if we do not employ the strategy method, and 160 non-student general population
Sample size (or number of clusters) by treatment arms
80 people per treatment
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Texas A&M University Institutional Review Board
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