Imitation, Institutions and Sustainability of Social Dynamics

David Chavalarias

CREA, Ecole Polytechnique, Paris

http://chavalarias.com

• Interacting components can reveal unexpected collective behaviour, properties and patterns.
• This emergent features can be sustainable in time and maintained by dynamic processes
• These emergent features can have highly non linear dependency with environmental conditions.

Thomas Schelling's model : example of emergent structures

• Consider a city with two populations speaking two different languages.
• People want to be able to speak their native language with at least a given proportion of their neighbours.
• If this proportion is under a given threshold, they try to move in a place where this condition is fulfilled.

Simulation of Thomas Schelling's model

Thomas Schelling's model

Result : Segregation arises even with a threshold below 40%.

Spatial segregation (emergent structures) might arise not because people don't want to live together but simply because they have a tolerance threshold on the percentage of neighbours speaking the same language.

A Simple model of fire percolation

• In function of the density of trees in a forest, a fire can spread or not.
• BUT, the damages caused by a fire is a non linear function of the tree's density.

A Simple model of fire percolation - Simulation

A Simple model of fire percolation

An example of non-linear dependency to environmental parameter

Result : around a given threshold, a small investment in forest maintenance can lower drastically the damages cause by fires.

A Simple model of fire percolation

Where else do we have percolation ?

• In soil diffusion (e.g. when extracting petrolum)
• In many biological systems
• Epidemiology (spread virus in human populations or Internet)
• In social systems : social contagion, strikes, diffusion of innovation, riots, fads, etc...

Important parameters

• Susceptibility toward contagion (depends on several factors like level of education)
• Neighbourhood configuration (density of people and communication channels - phone, sms, tv, etc.)

Isabelle Stengers distinguishes between models of reality and models of concepts.

We will deal in the following with models of concepts : how modelling can help us to think concepts and their different possible relations.

Thus previous example introduced concepts of percolation , non linearity and emergent patterns.

Two different perspectives

• Imitation causes desires : Tarde (1890), Baldwin (1890), Girard (1961), ...
• Desires cause imitation : a position often adopted by economics modellers (cf. Orléan 2002) but also mentioned by Tarde.

"Imitative desire is always a desire to be Another. There is only one metaphysical desire but the particular desires which instantiate this primordial desire are of infinite variety." René Girard Imitation of desires and believes in Tarde's work (1890), Girard's mimetic triangle (1961) Effect: convergence in desires

Girard's blind point : Everybody do not choose the same mediator.

Tarde and Baldwin : [The more and diverse suggestions we encounter, the weaker the intensity of each of them and the more the individual determines his choices after preferences from his own personality] Tarde 1890, The Laws of Imitation? Plus les suggestions de l'exemple se multiplient et se diversifient autour de l'individu, plus l'intensité de chacune d'elles est faible, et plus il se détermine dans le choix à faire entre elles, par des préférences tirées de son propre caractère [...]

«les causes sociales sont de deux sortes: logiques ou non logiques. Cette distinction a la plus grande importance. Les causes logiques agissent quand l'innovation choisie par un homme l'est parce qu'elle est jugée par lui plus utile ou plus vraie que les autres, c'est-à-dire plus d'accord que celles-ci avec les buts ou les principes déjà établis en lui (par imitation toujours).» Tarde 1890, The Laws of Imitation?

"Social causes are of two kinds : logical or not logical. Distinction is of highest importance. Logical causes act when an innovation is chosen by a man because it is judged by him more useful or more true than other, i.e. more in line than these latters with the goals already adopted by him (by imitation always).

We imitate after some personal criteria but since we can imitate criteria of others, we can change the way we imitate.

Imitation can change its own form

Chavalarias (2006) Metamimetic games: Modeling Metadynamics in Social Cognition, Journal of Artificial Societies and Social Simulations (JASSS) Vol. 9 Issue 2.

When some agents are still frustrated, we can still have counterfactual attractors.

Frustrated people are found at the border of social groups

Consider a population of agents in situation of dyadic social interactions with two opportunities of actions. Each interaction yields some material payoffs for the each protagonists Agents can view the worlds trough different imitation rules: Conformist Non-conformist Payoffs maximization Payoffs minimization

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