Of ants and Wall Street

Posted: July 27, 2009 in Uncategorized
Tags: , , , , ,

“Pop” explanations of emerging behavior (or emergence) usually begin with stories of insect colonies, flights of birds, hurricanes, stock exchanges and ecology.

All is meant to illustrate the fact that systems sometimes show properties that cannot be justified on the grounds of the properties of their components.

This fact is, in pop complexity literature and in the Wikipedias of sort, attributed to mysterious and capricious nature deviations. Exotic concepts such as “dissipative structures” are soon brought up, and the reader, often as long with her author, is lost.

What pop literature systematically fails to tell you is that properties that cannot be explained on the grounds of the laws that govern the components emerge from interactions between the components themselves, causing nonlinearity [1].

How it happens

The properties of a linear system are additive: the effect of a collection of elements is the sum of the effects when considered separately, and overall there appear no new properties that are not already present in the individual elements.

But if there are elements/parts that are combined, depending on one another’s, then the complex is different (not necessarily larger, as you will often read in pop literature) from the sum of the parts and new effects start to appear [2].

Although emerging behavior is easier to encounter in systems made of living organisms or in economic and social systems, it is important to realize that emergence appears in far more elementary contexts as well, such as particle or atomic physics, as Philip Warren Anderson started to show in the late ’60’s [3].

This very fact attests the importance of emergence at the epistemological level: on its grounds, a radical critique of reductionism can be developed, showing that the laws of particle physics are insufficient to explain the behavior of aggregates of electrons (like in superconductivity) or atoms, and that at each geometrical level (quark, neutron, nucleus, atom, molecule, virus, cell, etc.) new sets of laws may appear that, while compatible with the lower-level ones, introduce new knowledge.

The observation and study of emerging phenomena can get extraordinarily complex, especially when living organisms and populations are involved, and fascinating.

Clearly, mastery of the elementary foundations of emergence are needed if one is to analyze such phenomena of daunting complexity.

Ordinary examples

  • The particles that make up atoms do not have a colour. Protons or electrons aren’t green or yellow or red, because they do not absorb or emit visible light. Groups of atoms though, i.e. aggregates of those particles, do have colours
  • Many properties of condensed matter (ordinary matter), such as viscosity, friction or elasticity, are extraneous to the composing atoms and molecules. They emerge as properties of large aggregates of molecules
  • Barcelona, Inter or Manchester United are ranked with fantastic players, but not always do they win. A powerful, worldwide acclaimed soccer team can sometime lose to a minor provincial one. This happens because the behavior of the team as a system is not the mere sum of the potential of its parts, nor their isolated behaviors. Teamwork, strategy, tactics, group psychology (and luck) are all factors in winning a game. The problem is complex

[1] P.W.Anderson, “More Is Different”, Science, New Series, Vol. 177, No. 4047, August 4, 1972

[2] P.Bridgman, The Logic of Modern Physics, The MacMillan Company, New York 1927, pag. 42

[3] P.W.Anderson, ibid


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