Mass Replications & Extensions (CORE)

Quick jump to sections: BackgroundProject summary / Get involved: Join us / Resources / Publications & preprints / Media attention / Our team  / Completed replications  / Planned replications / Registered Reports


Project pages:



In 2016, following recent developments in psychological science (the so-called “replication / reproducibility crisis”) and gaining my academic independence, I decided to make major changes to my research agenda to prioritize pre-registered replications and pre-registered meta-analyses and focus on the realm of judgment and decision making. The aim was to revisit research findings I once took for granted and re-establish the foundations on which I hope to build my research. I, therefore, decided that all my teaching and mentoring work with guided thesis students will involve either pre-registered replications or pre-registered meta-analyses, atleast as a first step, to examine the classics in the field.

In 2017 I guided 3 masters students at Maastricht University to pre-test this realignment. It far exceeded my expectations. We completed 3 pre-registered replication, 3 pre-registered meta-analyses, and one review paper summarizing the insights gained.

Once joining HKU, in Dec 2017, I decided to scale up and mass-mobilize HKU’s undergraduate students and lead a massive pre-registered replication effort.

In the first 3 years of running this project, we’ve successfully completed ~100 replication projects, most of those with extensions, making this one of the largest replication efforts in social-psychology. For each of the projects, we have full pre-registrations, data/code, and all written up in APA style submission ready student reports. In the last semester, we focused on Registered Reports Stage 1.

If any of this is of interest to you – lots of ways to join in. I am looking for interested early career researchers to join us, see more info on that below.


I wrote a post for Psychology Today explaining my journey and why I’m doing this project – “Promoting the Credibility Revolution: The Journey to Open-Science“.


In January 2021 I gave a 3-hours workshop summarizing our 3 years of running the project and 100 replications milestone:


Workshop: Summarizing 3 years of collaborative open science and meta research with students and ECRs
Watch this video on YouTube.


If you want a shorter 45 minutes version, then I gave for a talk at Kent University in December 2020:


Collaborative “credibility revolution” open & meta science | Kent University seminar | Gilad Feldman
Watch this video on YouTube.


If you want the 5 minutes version, then in September 2022, I gave the following in the CloudResearch conference:

Large-scale replications & extensions of classic findings in social psychology & decision-making
Watch this video on YouTube.


Project summary

WARNING: Preliminary student summarized findings, need to be rechecked and verified. Only publications are verified.

I summarized findings in a poster in January 2021. Landscape version:

mass pre registered replication project status update portrait poster

Download the poster: PDF / PNG




Get involved: Join us

Are you an open-science early-career researcher and want to join?

Please see our detailed guide on how to join this project.

If you have any questions, please feel free to contact me and consider joining our mailing list.


Get involved: Resources

You’re invited to use or join us on any of the our many collaborative resources.

Please see dedicated resources page.

Publications & Preprints




Media attention

Media mentions of the project or related outputs:


Our team

A great team of open-science JDM Early Career Researcher collaborators joined us to finalize students’ reports for journal submissions:


Completed replications

WARNING: Preliminary student summarized findings, need to be rechecked and verified. Only publications are verified.

Note: Those completed replication projects in the table marked as “open” in grey are still available for you to join us and take lead.



Planned replications

Note: Those in the table marked as “RRS1 done, need lead” are completed Registered Report Stage 1 manuscripts, completed with simulated datasets and planned data analysis code, with ready manuscripts based on our templates, looking for leads ECRs to help us submit those to journals as Stage 1 and carry these all the way through an in-principle acceptance till a successful Stage 2 publication.

Those in the table marked as “open” in red are still available for guided thesis students and interns.




Related JDM mass-replication initiatives

There are two related initiatives conducting mass replications of JDM findings:

  1. The Hagen Cumulative Science Project
    1. How to Teach Open Science Principles in the Undergraduate Curriculum (preprint)
  2. Replicability and Reproducibility of heuristics and biases in Judgment and Decision Making (RR-JDM) @ Linköping University by JEDI lab


Other open-science projects






Who is involved?


So far involved in this project:

Big thanks to all involved students and teaching assistants.


How to cite this project?

Please cite as the following:

Collaborative Open-science REsearch (2022). Replications and extensions of classic findings in Social Psychology and Judgment and Decision Making. DOI 10.17605/OSF.IO/5Z4A8. Retrieved from and