6 Mar 2021

Phase transition in swarm formation

Posted by jofr

In physics there is a phase transition between a gaseous state where every molecule moves in isolation, a liquid state where loosely coupled molecules flock together and a solid state where strongly coupled molecules stick together permanently in a rigid way. The direction from gas to fluid is called condensation, the opposite direction is called vaporization.

Swarm formation in a social system which is composed of many independent agents is like a phase transition from gaseous to liquid state. There is a (second order) phase transition for actors between a state where everyone acts in isolation and follows his own intentions, and a collective state where actors in a swarm stick together like fluid molecules in a bubble and eventually form a group.

When does the transition happen? The group cohesion in a swarm obviously changes depending on how well the group building rules are known and applied. If the cohesion of the group crosses a critical threshold, groups start to emerge and isolated actors condense to a group, or they start to dissolve again and the group vaporizes. If a group forms at all and what properties it has depends on how tightly or loosely the agents adhere to social norms that keep the group together.

The critical parameter if a phase transitions happens is not temperature or pressure as in the case of fluids, but the period of the teaching interval, which is a measure for rule adherence if the agents are forgetful actors that need to be taught regularly. Here is a simulation result from my book “Hidden Genes” which describe the phase transition depending on the teaching interval. Have you ever wondered why all major Abrahamic religions require a weekly meeting at a 7 days interval where the rules are taught? Well, without these meetings people originally would start to forget the rules and the group would dissolve – or vaporize like a bubble that turns into gas.

Once a swarm has formed, it has certain properties. A liquid maintains a fairly constant density and viscosity, a group maintains a certain cohesion. As Michele J. Gelfand has argued we can distinguish between tight cultures which adhere strictly to collective rules and social norms, and loose cultures which adhere less tightly to the rules. Is this helpful to complete an evolutionary view of life, as David Sloan Wilson argues in his recent book? I think yes.

( Droplet image by ju Irun from Pixabay )

* Michele J. Gelfand, “Rule Makers, Rule Breakers: How Tight and Loose Cultures Wire Our World”, Scribner, 2018
* Michele Gelfand on Tight and Loose Cultures in a TVOL Interview with David Sloan Wilson
* David Sloan Wilson, “This View of Life: Completing the Darwinian Revolution”, Pantheon, 2019

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