SFB 504 discussion paper No. 03-04:

No imitation—on local and group interaction, learning and reciprocity in prisoners' dilemma experiments

Oliver Kirchkamp and Rosemarie Nagel


This study disentangles experimentally imitation, reinforcement, and reciprocity in repeated prisoners' dilemmas. We compare a simple situation in which players interact only with their neighbours (local interaction) with one where players interact with all members of the population (group interaction). We observe choices under different information conditions and estimate parameters of a learning model. We find that imitation, while assumed to be a driving force in many models of spatial evolution, is often a negligible factor in the experiment. Behaviour is predominantly driven by reinforcement learning.

JEL-Classification: C72, C92, D74, D83, H41, R12

Keywords: Local interaction, experiments, prisoner's dilemma, reinforcement, repeated games.