Complex play behaviors emerge in social mammals, such as primates, cetaceans (whales and dolphins), and some carnivores. This stage involves social play, object play, and play that strengthens social bonds, such as mock wrestling and playful grooming.

The rise of larger brains and more intricate social structures in this period creates a need for advanced cognitive skills and social learning. Play evolves as a tool for developing cooperation, communication, and emotional regulation.

Social play becomes a key feature of mammals with advanced cognition, laying the groundwork for behaviors like role-playing and creative problem-solving. These traits appear most prominently in primates, whose social hierarchies and group dynamics depend on learned behaviors.