To describe social relationships in animals, biologists usually rely on game theory. But this mathematical description of decision-making behavior is too rigid to capture the complexity of social relationships between animals. A new model changes that.
“Based on observations, biologists have developed all kinds of complex ideas about social relationships between animals,” says Professor Olof Lemar (Stockholm University). He specializes in applications of game theory to biology. But these social connections do not fit into game theory, which is limited to interactions between two individuals and their mutual transactions in the short run. Social relationships are more complex than this, develop over time, and involve a large number of interactions. Moreover, bonds grow in the context of a group, not just between individuals.
To arrive at a model that better reflects observed behavior, Lemar and his colleagues brought insights from animal psychology to game theory. They tested this against data on social behavior in vampire bats. “Vampire bats are social animals, for example, they gather in large groups and share food. Mutual hierarchies are less strong than in primates, and they are also easier to study than, say, dolphins. That's why we know so much more about their social lives.”
Animal psychology
The model developed by Lemar focuses on the conditions under which social relationships among group members foster cooperation. “Our new model fits observations more closely, explaining how they emerge gradually based on a history of mutual favors and recently shared activities. It combines elements from animal psychology and game theory, and more specifically the Rescorla-Wagner model. This describes how the strength of the association grows between Different stimuli during the learning process. Similar to this rule, social ties in our model grow from the exchange of help and services over time. The strength of those social ties in turn determines who gets what.
Based on observations of vampire bat behavior, Lemar included other elements in his model. “To help other animals, small social units are needed. These can just as easily be subgroups within a larger whole. In specific terms: Vampire bats stay in groups of up to four thousand individuals during the day, but the animals form small groups in that large swarm to which they continually return. Aid in the form of food is also shared more quickly with members of one's “friend group.” When two groups come into contact with each other, individuals avoid forming social bonds with members of the other group. Surprisingly, there is a tendency to do so with New individuals.
