# Social identity and cooperation co-evolve in a multilevel public goods game

## TL;DR

This study shows how social identity and cooperation at different levels interact, influencing people's decisions in collective action scenarios.

## Contribution

The paper introduces a novel experimental approach to study multilevel cooperation and social identity dynamics.

## Key findings

- Local cooperation options reduce global cooperation and increase parochial biases.
- Higher payoffs for global cooperation lead to increased global cooperation levels.
- Successful group cooperation enhances social identification with the group.

## Abstract

In the real world people often face collective action problems at multiple scales, where they must choose between local and global cooperation. Unlike single public goods scenarios, which can be solved if enough players are willing to cooperate, multilevel collective action problems introduce an additional coordination challenge in working towards the same goals. Using a pre-registered, online behavioural experiment, we investigate how perceptions of social identity predict and covary with cooperation success in multilevel public goods games. We find that introducing a local cooperation option undermines global cooperation and exacerbates parochial biases, but that increasing the payoffs of global cooperation boosts global cooperation levels. We also see a performance-cohesion effect, whereby successful cooperation within groups is associated with increased social identification with that group. Overall, our findings point to the importance of social context for cooperation, social identity, and their interplay.

The online version contains supplementary material available at 10.1038/s41598-025-30979-2.