Working memory constrains human cooperation in the Prisoner's Dilemma

Area of Science:

• Evolutionary Game Theory
• Behavioral Economics
• Cognitive Psychology

Background:

• The evolution of cooperation is a key problem in social sciences, often modeled using the Iterated Prisoner's Dilemma.
• Theoretical models predict that memory capacity influences cooperative strategies, but empirical tests in humans are limited.
• Previous simulations suggest natural selection can favor cooperation in the Prisoner's Dilemma.

Purpose of the Study:

• To empirically test whether human strategies in the Iterated Prisoner's Dilemma align with theoretical predictions based on memory capacity.
• To investigate the impact of working memory constraints on the adoption of cooperative strategies.

Main Methods:

• Human participants played the Iterated Prisoner's Dilemma game under two conditions: continuous play and play interrupted by a working memory task ('Memory' game).
• Working memory capacity was manipulated by the secondary 'Memory' task, constraining recall of previous game rounds.
• Observed strategies were categorized and compared between the continuous and interrupted conditions.

Main Results:

• In continuous play, participants predominantly used 'Pavlovian' strategies, consistent with higher memory capacity predictions.
• When working memory was constrained by the 'Memory' game, the proportion of 'generous tit-for-tat' strategies increased, as predicted.
• A trade-off was observed: complex Pavlovian strategies were less successful in the memory task but more successful in the Prisoner's Dilemma game.

Conclusions:

• Human cooperative strategies in the Iterated Prisoner's Dilemma are sensitive to working memory capacity.
• Findings support game-theoretic predictions regarding the evolution of cooperation under varying memory constraints.
• The study demonstrates a cognitive trade-off influencing strategic decision-making in social dilemmas.