KONSTANZ, Germany — Just because someone’s being selfish, doesn’t mean they’re automatically being unfair. This hypothesis, which actually dates back to the 1970s, has now been confirmed by physicists from the University of Konstanz in Germany.
“Surprisingly, when individuals act out of pure selfish reasons, this can lead to a fair situation within the group,” says physics professor Clemens Bechinger, in a statement.
It started with W.D. Hamilton in 1971. He proposed the idea that individuals within a herd reduce their risk of being predated by positioning themselves in a specific way that only benefits them, and not their neighbors.
Herd-gathering behavior is nothing new in the animal kingdom. For example, seals on their own make for an easy target for orcas and sharks, but if they’re together in a group, they’re less likely to get caught easily. The seals gathered in the center will be harder to reach, and attacking them will be more work for the predators. But around the edges, seals here have the short end of the stick and are more likely to get eaten. This explains why animals often try to scurry for the middle spots.
To explore this, Clemens and his colleagues used AI reinforcement learning technology to explore how individuals have to position themselves optimally to lessen their own risk of being attacked.
“Considering reinforcement learning for collectives opens up a range of new possibilities in understanding animal behavior,” Iain Couzin, speaker of the CASCB and Professor for Biodiversity and Collective Behaviour at the University of Konstanz adds. “It provides an elegant way to ask how adaptive behaviors may emerge in the complex social context characteristic of flocks and swarms.”
Consistent with the 50-year old hypothesis, the physicists saw that individuals that were spread out at first and then formed a herd reduced their odds of being attacked, by coming closer together. “Because this strategy increases the risk for neighbors, it is clearly considered a selfish motivation,” says Veit-Lorenz Heute, who is working as a doctoral student on the project.
But to the team’s surprise, things didn’t stop here. Their simulation also showed that the time-averaged predation risk is exactly the same for everyone. This is because although individuals in the middle have the coveted spot, others are constantly pushing them for it, and those already there can’t defend their spot. As a result of this “Hunger Games” of sort, the group began to rotate around the gravitational core, which is something commonly observed in animals that herd together in the wild.
“Our study shows that the formation of groups does not necessarily result from their gregarious behaviors but can also be explained by the entirely selfish motivations of individuals to gain an advantage at the expense of others,” Bechinger concludes. “Not only does our study help to understand collective behaviors in living systems, but the results may also be useful in the context of finding optimal strategies of how autonomous robotic devices have to be programmed to master collective tasks.”
The findings are published in the Journal of Theoretical Biology.
