Last week, I attended a seminar about “Understanding and Managing Complex Systems” organised by the Royal Netherlands Academy of Arts and Sciences (KNAW) together with the Netherlands Organisation for Scientific Research (NWO). The take home message from this seminar is that 1) Complex Systems are highly popular in Amsterdam, all the 200 available seats where taken the day the registration was open and 2) Complex Systems is the science of cooperation.
In a first session, Martin Nowak explained in a very good talk that 5 different cooperation mechanisms can be observed in an evolving population. 1) Direct reciprocity: individuals cooperate if the individuals they interact with are cooperative (“Tit for Tat“), 2) Indirect reciprocity: based on reputation, this motivate cooperation by the social gain to be expected. Cooperators gain reputation points and became known as cooperators in the networks. This important mechanism could not survive without extended communication capabilities making it possible to diffuse this reputation. 3) Spatial distribution: cooperation (and defection) is better achieved in cluster of individuals, both behaviors can co-exist within different clusters of individuals. This connects with 4) Group selection: there is a multi-level aspects of group selection, infections at one scale can have more impact on another. Lastly, 5) Kin selection, Nepotism: individuals tend to cooperate more with others close to their kin and defect those that are less similar. Then, Kees Stam explained how the brain exhibits small world and scale-free properties. It is also modular with several zones dedicated to particular tasks and cooperating. Mental disorders, and also the effect of aging, maps to changes in the connectivity between the different hubs in the network. Although these results where observed on simplified networks, a full model of the network of a brain – with all its neurons – it’s on its way to be created. That will be a huge network to study!
During the second session, Dan Braha gave a fantastic talk on the importance of the in and out degree of the nodes in a network. The notion of hubs and the global degree are not enough to explain network responses and the study of the covariance between in and out degrees can provide better insights on the dissemination of messages along the connections. This talk was followed with that of Michael Batty who described the evolution of cities and some models to predict their growth and increase in complexity.
The day concluded on a pleasant musical session with Marten Scheffer playing and inviting us to reflect around the topic of complexity and interaction within our civilizations.
Update: the presentations are now visible online