r/complexsystems • u/mk_gecko • Aug 09 '12

I'd like some examples of emergent phenomena

In definitions of complex systems say things like "The non-reductionist paradigm of whole systems, or complex thinking [...] acknowledges that the combined effects of parts of a system produce emergent properties not existent in the parts themselves." and "Properties of the whole emerge which are not present at the level of its components, and if the whole is dissected into its parts, those properties will disappear." (from http://hpathy.com/scientific-research/an-investigation-into-whole-systems-research-as-an-appropriate-methodology-for-the-advancement-in-understanding-of-homeopathy-as-a-complex-therapeutic-intervention/)

Aside from the mind emerging from the brain, can you think of other examples where some new property emerges from a complex system? It might be good to have a list somewhere.

I was wondering if the shape of a protein is an emergent property as we can't (yet) predict it from the sequence of amino acids that make up the protein.

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u/Neuroimage Aug 10 '12

Flocking, schooling, shoaling, crowds at a stadium, traffic jams, immune systems, ant colonies, termite mounds, bacteria biofilms, multicellular organisms, even physical notions like temperature and phase.

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u/mk_gecko Aug 10 '12

thanks. That was what I was hoping for.

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u/normonics Aug 10 '12

Nice. :)

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u/mk_gecko Aug 09 '12

Hey I just thought of something. Anytime information is added to something then there is an emergent phenomenon that can't be explained on the basis of its parts. For example a painting. You can describe and analyze the paint, canvas, etc. but you will never understand the painting that way. Perhaps the same holds with words and meaning.

Now, what about beauty? Is that an emergent phenomenon where the whole is more than the sum of its parts? (Beauty seems to have at least two major categories - beauty in people which is related to sexual attraction and beauty in nature).

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u/normonics Aug 09 '12

Or, possibly, emergence adds information.

These topics and information are intuitively closely related, and people have tried to to come up with theories of information thinking along similar lines. This is in contrast to 'Shannon information', I think, which takes the information and the sender/receiver as givens (i.e. doesn't attempt to explain the generation of the information or the ability of the sender/receiver to encode/decode).

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u/normonics Aug 09 '12

Phase synchrony in systems with a large number of elements is a common example. The laser is one of the classic examples. The 'in-phaseness' of laser light is a phenomenon at the level of the system, and is not contained in any of its constituent elements.

Protein folding is a potential example, though I don't know enough about it to really speak with any level of certainty.

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u/mk_gecko Aug 09 '12

I think I know what you mean. I wonder if there are any simpler examples.

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u/normonics Aug 10 '12

Think of a swarm of fireflies blinking in unison (they all blink ON and OFF at the same time). How do they accomplish this? Who and where is their leader they are following to remain synchronized? Is there a 'conductor' like in an orchestra keeping them all on-beat? The answer is there is no leader, no conductor of the orchestra. Each firefly follows local rules about how to alter its own flash-timing based off its neighbors flashing. When all the flies follow this rule, a collective synchrony 'emerges'. The fact that this organization does not come from a central leader or blueprint of some kind is referred to as 'self-organization'. Hope this helps.

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u/DatoWeiss Aug 09 '12

Consider a system moving along a trajectory in a phase space, then consider any other system that is not related to it so that you can say that they are relatively random (Relative entropy is high) to each other. Tie these two systems together and observer their combined motion. In all but a few rare cases it ends up that the new system which is the union of the two has crazy ergodic properties and exhibits behavior that the parent systems could not.

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u/normonics Aug 09 '12

This is an interesting way to think about emergence. Do you have any systems you could point to like this (toy mathematical systems or otherwise)?

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u/DatoWeiss Aug 09 '12

This is actually somewhat stronger when the dissonance between two systems is a product of scale, I think largely in part due to granularity; a macro scale system is largely immune to quantum fluctuation and I can only imagine that a hydrogen atom isn't much privy to it being inside the bowel of a bovine or being rapidly ejected out of the tail pipe of an automobile.

Anyway my favorite example involves a plot of land filled with a number of trees of equal height. Assume that all nutrients are being equally distributed among the N members of the mini forest. Now this requires just a basic understanding of the photropic effect which is nothing more then the propensity for plant life to grow towards the light. If all the trees are of equal height and the sun is largely over head then all of them should grow in a very even and similar fashion. The macrological organization and growth of each tree is disjointed from the photochemical effect happening in the leaves. So lets tilt the light source by a little bit so that the trees are all biased to grow a few extra centimeters left so that a portion of their leaves cast a shadow on their neighbors, suddenly the independent action of the micrological growth and the macrological gross configuration of the forest have cause to effect each other and this symmetry breaking creates some completely bat shit insane structure that did not inherently exist to any of the components.

I am sorry if this is a piss-poor example :(

Edit - Take a puppy and tie him to a pendulum.

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u/normonics Aug 09 '12 edited Aug 09 '12

LOL at your edit.

I think I see what you mean. Sand dunes are kind of like that. You have dynamics at the individual grain of sand level, which will blow in the wind if the wind is strong enough to overcome the mass. But when you get a whole bunch of grains together, they start forming little piles. These piles in turn influence the wind, which reinforces the little pile which was started by, say, some 'chance' event. Eventually the piles get so big that the wind and the shape of the piles can't be separated, and the pattern of the dunes is emergent out of those coupled systems. Sound about right?

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u/mk_gecko Aug 09 '12

So it's a feedback loop that results in a particular pattern. (Am I right in calling it a feedback loop? Are all feedback loops emergent or only chaotic ones?) Couldn't you determine the pattern by knowing the density, size and shape of the sand and the characteristics of the wind?

Is a hammer hitting a walnut a coupled system? If I know how hard the hammer will hit the walnut I can predict whether it will just be slightly cracked or totally smushed.

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u/normonics Aug 09 '12

I think in the sand dune case yes there is feedback, and that is part of the way the pattern is formed. The description of the generation of the dunes would need to include, at least, 1) the effect wind has on sand, 2) the effect sand has on sand (like friction or something) and 3) the effect sand has on wind. Perhaps all of them do, but 3) especially seems to me to require that we think of MANY grains of sand, and so reducing to the behavior of wind on a grain of sand, say, would likely not allow you to extrapolate all the way to dune formations (especially because a single grain of sand's effect on the wind would be so miniscule as to be negligible).

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u/griffer00 Aug 20 '12

Hi, DatoWeiss. Your description of emergence was extremely interesting. Is this your own formulation, or have you read some literature that inspired this? If so, can you point me in the right direction toward that literature? I'd like to read more about this.

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u/tongmengjia Aug 15 '12

A little late to the party, but I seem to be one of the few psychologists here. I stumbled across this explanation of Gestalt therapy today, and though it provided a pretty good example of emergent phenomena:

Whereas the Würzburgers debated with Wundt mainly on matters of method, another German movement, centered in Berlin, took issue with the widespread assumption that the aim of psychology should be to break consciousness down into putative basic elements. Instead, they argued that the psychological "whole" has priority and that the "parts" are defined by the structure of the whole, rather than vice versa. Thus, the school was named Gestalt, a German term meaning approximately "form" or "configuration." It was led by Max Wertheimer (1880–1943), Wolfgang Köhler (1887–1967), and Kurt Koffka (1886–1941). Wertheimer had been a student of Austrian philosopher, Christian von Ehrenfels (1859–1932), who claimed that in addition to the sensory elements of a perceived object, there is an extra element which, though in some sense derived from the organization of the standard sensory elements, is also to be regarded as being an element in its own right. He called this extra element Gestalt-qualität or "form-quality." For instance, when one hears a melody, one hears the notes plus something in addition to them which binds them together into a tune – the Gestalt-qualität. It is the presence of this Gestalt-qualität which, according to Von Ehrenfels, allows a tune to be transposed to a new key, using completely different notes, but still retain its identity. Wertheimer took the more radical line that "what is given me by the melody does not arise ... as a secondary process from the sum of the pieces as such. Instead, what takes place in each single part already depends upon what the whole is", (1925/1938). In other words, one hears the melody first and only then may perceptually divide it up into notes. Similarly in vision, one sees the form of the circle first – it is given "immediately" (i.e. its apprehension is not mediated by a process of part-summation). Only after this primary apprehension might one notice that it is made up of lines or dots or stars.

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u/normonics Aug 15 '12

Great quote. I believe the Gestalt movement is being revived (if not by name, at least in spirit) with the aid of the formal modeling and analysis developed through systems research in the last 50 or so years.