Understanding social hierarchies in mice
From playground dynamics to corporate hierarchies, social ranking influences access to resources, mating opportunities, and territory. Researchers at the Okinawa Institute of Science and Technology (OIST) are shedding light on the brain mechanisms that underlie these dynamics in male mice. Their work points to specific neural circuits that govern how past experiences shape future social status, revealing a nuanced picture of dominance that goes beyond size or strength.
How scientists determine dominance in mice
The team used dominance tube tests to map social structure within groups. In these experiments, two mice face each other at opposite ends of a tube; the one that gains the right of way is deemed more dominant. Repeating these encounters over days identifies stable leaders and subordinates in a mouse colony.
To explore how social standing shifts, researchers paired mice so that dominant individuals competed against other dominants, and subordinates against subordinates. Results showed that past performance could predict future status: winners tended to stay or become more dominant, while losers often slipped in rank. This phenomenon is described as the winner- and loser effects.
Lead author Dr. Mao-Ting Hsu explained, “Those with experience of winning become more dominant in future competitions, and those who lose become less dominant.” The team set out to uncover the neural underpinnings of these effects, with a particular focus on how losing reshapes decision-making in social contexts.
The brain circuitry behind the loser effect
The researchers turned their attention to the basal ganglia, a brain region long associated with action selection and behavioral flexibility. Within the dorsomedial striatum, they identified cholinergic interneurons as key players in how animals adjust after losses.
To test causality, the team selectively removed these cholinergic interneurons. The result was striking: the loss-related decrease in social rank (the loser effect) disappeared, suggesting that these neurons are necessary for losers to adjust their future behavior based on past outcomes. In contrast, removing the same neurons did not alter the winner effect, indicating that different circuits may support rewards-based learning during wins.
The findings imply that winning and losing engage distinct neural processes: the winner effect likely involves reward-based learning, while the loser effect relies on decision-making processes that weigh context and prior experience. This dissociation adds depth to our understanding of social behavior, showing that flexible adaptation to social environments can hinge on specific cell types within a familiar brain network.
Why this matters for understanding human social dynamics
Although the study focused on male mice, the implicated brain circuitry—part of the basal ganglia—shares notable similarities with humans. The researchers suggest that the neural strategies animals use to decide when to pursue dominance, and how to react after losses, may echo human social decision-making in varying environments, from family life to workplaces.
“Human social dynamics are obviously far more complex,” said Dr. Hsu. “There is little evidence of the brain circuitry involved in these flexible social behaviors in humans. However, the similarities in brain structure between mice and humans mean these studies could offer a window into how our own social decisions are sculpted by prior experiences.”
Looking ahead
These insights into the loser effect open avenues for exploring how social experience interacts with neural plasticity across species. Beyond basic science, the findings could inform research into conditions marked by social and decision-making difficulties, by clarifying how specific neurons contribute to context-dependent behavior. As science continues to map the brain’s social algorithms, studies in mice provide a valuable bridge to human neuroscience and the study of complex social life.
