Neural processing of iterated prisoner’s dilemma outcomes indicates next-round choice and speed to reciprocate cooperation

ABSTRACT

The iterated prisoner’s dilemma (iPD) game is a well-established model for testing how people cooperate, and the neural processes that unfold after its distinct outcomes have been partly described. Recent theoretical models suggest evolution favors intuitive cooperation, which raises questions on the behavioral but also neural timelines involved. We studied the outcome/feedback stage of iPD rounds with electroencephalography (EEG) methods. Results showed that neural signals associated with this stage also relate to future choice, in an outcome-dependent manner: (i) after zero-gain “sucker’s payoffs” (unreciprocated cooperation), a participant’s decision thereafter relates to changes to the feedback-related negativity (FRN); (ii) after one-sided non-cooperation (participant wins at co-player’s expense), by the P3; (iii) after mutual cooperation, by late frontal delta-band modulations. Critically, faster reciprocation behavior towards a co-player's choice to cooperate was predicted, on a single-trial basis, by players' P3 and frontal delta modulations at the immediately preceding trial. Delta-band signaling is discussed in relation to homeostatic regulation processing in the literature. The findings relate the early outcome/feedback stage to subsequent decisional processes in the iPD, providing a first neural account of the brief timelines implied in heuristic modes of cooperation.

KEYWORDS:

• Social heuristics
• prisoner’s dilemma
• delta
• P3
• FRN

Acknowledgments

This work was supported by the grants Proyectos I+D from the Comisión Sectorial de Investigación Científica (UdelaR), and Fondo Santiago Achúgar Díaz 2018 (Uruguay) to V.B.G, from the Agencia Nacional de Investigación e Innovación (Uruguay) to F.C.C., Ayudas a la Atracción de Talento Investigador and Proyectos I+D para Jóvenes Investigadores from the Comunidad de Madrid and Universidad Autónoma de Madrid (Spain) [2017-T2/SOC-5569; SI1-PJI-2019-00011] and Proyectos I+D from the Ministerio de Ciencia, Innovación y Universidades (Spain) [PGC2018-093570-B-I00] to D.K. We thank funding support from ANII and Programa de Desarrollo de las Ciencias Básicas to A.C. and V.B.G. We also would like to thank the anonymous reviewers of this manuscript for their comments and suggestions.

Disclosure of interest

The authors report no conflict of interest.

Data availability statement

The data that support the findings of this study are openly available in Open Science Framework at http://doi.org/10.17605/OSF.IO/G8Z7Y

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was funded by the Agencia Nacional de Investigación e Innovación (Uruguay) [PD_NAC_2018_1_150365]; Comunidad de Madrid and Universidad Autónoma de Madrid (Spain) [2017-T2/SOC-5569; SI1-PJI-2019-00011]; Ministerio de Ciencia, Innovación y Universidades (Spain) [PGC2018-093570- B-I00].