7.2 Emergent Phenomena

From ants to galaxies, studies of complex physical systems have revealed that surprising phenomena can often arise on the whole when a large number of components interact according to very simple rules. In the context of causation, we encourage students to consider emergence, rather than purposeful orchestration, as a possible causal explanation of certain societal phenomena, such as sudden market crashes and the virality of misinformation on social media.

The Lesson in Context

After discussing more concrete forms of causation, we now introduce a type of causation whose outcome is not measured on an individual level, nor on a statistical level (e.g. averaging over individuals). In emergent phenomena, the outcome cannot be found by measuring any number of individuals, but is purely a property of the entire system. We tie this concept of causation to society by recognizing that many sociological phenomena may be of this type.

Relation to Other Lessons

Earlier Lessons

1.2 Shared Reality and Modeling

• The idea of emergent phenomena calls back to the "raft vs. pyramid" descriptions of science. From a reductionist viewpoint, all our understanding breaks down when we end up being wrong on a smaller scale. However, scientists may work on problems at different scales of explanation and still have meaningful results. Harkening back to the raft viewpoint, the areas where these explanations overlap should be consistent. If the explanation at any scale turns out to be wrong, it does not automatically invalidate the other scales.

7.1 Causation, Blame, and Policy

• Singular causation is individual intervention leading to an individual result. General causation is the same intervention on many individuals leading to results on these individuals that can be seen only statistically. Neither cover the case where the result is purely a property of the whole system, rather than any number of individuals.
• When something goes wrong in society, we may blame a particular leader or policy. This is can be helpful in determining how to intervene for future prevention. However, one shouldn't overlook the possibility that the cause is emergent, and therefore the blame may be misplaced.

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Later Lessons

8.1 Orders of Understanding

• When deciding what simple objects and rules to include in a model of an emergent phenomenon, it is helpful to separate the first-order causes from the higher-order ones. For example, in modelling the persistent traffic jams on highways as an emergent phenomenon, we do not include honking.

Takeaways

Learning GoalsDefinitionsExamplesCommon Misconceptions

After this lesson, students should

1. Understand that simple things governed by simple rules can, in aggregate, result in surprisingly complex behaviors, which can be studied in and of themselves.
2. Be aware of when complex behaviors in some physical and sociological systems may be the consequence of relatively simple rules on the constituents, and therefore not fully explicable by either reductionism or deliberate agents.
3. Be aware of humans' tendency to over-perceive agency in external phenomena in general (e.g. anthropomorphizing), making us prone to mistaking emergent phenomena as intentional.
4. Understand that there is value at larger and intermediate scales of explanation despite the fact that larger scales may be reducible to smaller ones.

Scale of Explanation

The scale of the objects we're describing in a system and of the phenomena that emerges from their interaction. This is also called a "level" of explanation. For example, human interactions can be explained at various scales: On the scale of genetics and neurochemistry, on the scale of cognition and behavior, or on the scale of society and culture.

Emergent Phenomenon

A (sometimes surprising) phenomenon that's observed on a large scale due to the interaction of a large number of small constituents (often referred to as "agents") interacting with simple rules. (Note that these objects and rules may also be emergent due to interactions on an even smaller scale.)

Phase Transition

A point where a slight change in the small constituents or simple rules in a system cause a dramatic change in the behavior of the system as a whole.

Scientific Reductionism

A viewpoint that says the purpose of science is to look for the smallest possible (most "fundamental") components of a system that everything else is made of. This viewpoint overlooks that knowledge can be gained from considering objects at larger scales without referencing their smaller constituents. For example, we want to be able to program computers without having to reference the states of their constituent transistors, and treating depression at the level of relationships, environment, and cognitive habits can be more effective than considering the level of neurochemistry, although both are relevant.

Social media

When people are highly connected to each other in social networks with simple rules of interaction (likes, friending, retweeting, etc.), unintended emergent phenomena, such as widespread misinformation, are likely to arise.

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Water

Water is wet, but water molecules are not. The property of "wetness" must emerge from the relatively simple rules that govern the interactions between water molecules.

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Conway's Game of Life

A classic demonstration of cellular automata, in which simple local rules result in complex patterns arising on a larger scale.

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Schelling Model of Segregation

A model wherein large scale racial segregation can emerge even when individual people have no explicit desire to segregate. When the agents are fine being in the minority as long as at least some fraction of people that live around them are of the same group, even this mild preference can lead to segregation.

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Consciousness

Consciousness as a result of local interactions between neurons.

YouTube is promoting late night talk show hosts over smaller individual creators. It must mean that the YouTube executives are deliberately stifling small content creators.

While such a conspiracy is still possible, it is also likely that the rules that govern the recommendation algorithm result in this emergent phenomenon, when it was not the executives' explicit intention.

An arrogant physicist would say that all your thoughts and emotions are nothing more than complex interactions between subatomic particles.

Sure, this may be true in principle. But, describing thoughts and emotions purely in terms of subatomic particles skips so many scales of explanation so as to be fairly useless for understanding how to get about in the world as a person.

"Let's say chess is the rules of the universe. After two thousand years, we finally figured out how the pawns move. And then I suppose one day we'll have the God equation and that'll tell us how the whole chess board moves and then we'll become grand masters." -Michio Kaku

Just as knowing the rules of chess doesn't make one a grand master, simply knowing the fundamental laws of physics doesn't give one a full understanding of all things. One needs explanations at every scale, especially if one wants to be able to intervene at the scale we perceive (which is not the scale of atoms).

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