The data

All papers included in CoDa are about cooperation in social dilemmas, as exemplified by three prototypical social dilemmas…


Prisoner’s Dilemma

A situation that involves a conflict of interests, in which individuals decide independently whether to cooperate (transfer any portion of their endowment to the partner) or defect. The transfer is multiplied by a constant m (m > 1) and added to the partner’s endowment. Each person has an incentive to defect, but if everyone defect, then each person receives a worse outcome compared to when everyone cooperates.

Dolor sit amet

Public Goods Dilemma

A situation that involves a conflict of interests, in which each member of a group of size N decides how much of an individual endowment to contribute to a group account G. Two (or more) people decide (how much) to contribute to a public good. Any amount contributed to the public good is multiplied by a constant m (1 < m < N) and  is equally distributed to all group members, regardless of their contribution.


Resource Dilemma

A situation that involves a conflict of interests, in which each member of a group of size N decides how much to withdraw from a common resource. The amount each member takes is no longer available to other group members. The resource pool is replenished by a specific rate r (r > 1), and people can continue to consume the resource until it is depleted.

How did we search for studies?

CoDa contains annotated studies on human cooperation reported in published articles, working papers, dissertations, theses, and book chapters written in English, Japanese, and Chinese. These documents were retrieved as a result of a systematic literature search in September and October 2015, as well as in January 2018, using PsychInfo, Web of Science, Google Scholar, and online University library repositories (VU, Leiden) for English documents. The search for Chinese documents was conducted from November to December 2017 using CNKI, Wangfang Data, and CQVIP. The search for Japanese documents was conducted from July to December 2018 using Cinii. Additional studies were included as a result of a call for missing published studies, September 2019.


How did we select studies?

Many studies were retrieved as a result of the systematic search, but not all of them are included in CoDa. To be included, the studies had to involve human participants interacting in a prisoner’s dilemma, public goods dilemma, or resource dilemma. Additionally, in order to be included the studies had to report the amount of oberserved cooperation in the sample or enough quantitative information to allow computation of effect sizes.

Flowchart coda pic


The generated dataset is hosted in a TriplyDB graph database and can be accessed here.

Learn more about the search and selection of studies

What was annotated in the studies?

Annotate 1

Paper Meta-data

  • Title
  • Doi
  • Authors
  • Year of publication
And more
Annotate 2

Sample Characteristics

  • Sample size
  • Country
  • Mean age
  • Percentage of males
And more
Annotate 3

Study Characteristics

  • Type of social dilemma
  • Repeated interactions
  • Group size
  • Degree of conflicting interests
And more
Annotate 4

Quantitative Results

  • Mean cooperation
  • Standard deviation
  • Rates of cooperation
  • Effect sizes
And more
Ontology pic

Variables that predict cooperation

We coded for all possible variables, measured or manipulated, that have been used in past research to predict cooperation. Browse our codebook to learn more about these variables.

We developed an ontology of human cooperation studies, which consists of a graph of concepts and their relationships, describing the properties of published papers, studies, and experimental results.

An ontology is a body of formally represented knowledge in the form of concepts – including the relationships that hold among them – that exist in an area of interest. Ontologies are represented in the form of graphs of nodes and edges, where the nodes correspond to concepts of the domain, and the edges correspond to attributes of a concept or relationships between concepts.

CoDa offers an Ontology explorer tool on the CoDa platform.

Browse Codebook

Updates and bug fixes

CoDa is work in progress. Your feedback helps us improve the data and research platform. For information on updates and bug fixes, please see the change log.

Please note that updates may change the results obtained through the CoDa research platform.

Change log