Download Levels of Organization and Causation

Levels of Organization and
Causation
PSC 113
Jeff Schank
Outline
• Levels of Organization
– Composition
– Interactions
• Time Scale
– Composition
– Interactions
•
•
•
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Complex Systems
Complexity and Levels of Organization
Scientific Perspectives and Organization
Causation
– Aristotle’s Four Causes
– A Reformulation of Aristotle’s Four Causes
• Army Ants
First an Example
• Fall Webworms
Levels of Composition
• A thing X is at a higher level of composition
than a thing Y if X is composed of Ys (and
possibly other things)
• For example,
– A brain is at a higher level of composition than a
neuron because brains are composed of neurons
(among other things)
– A cell is at a higher level of composition than DNA
molecules, because among other subcellular
structures, cells are composed of DNA
Levels of Composition
Levels of Composition
Interactions
• Levels of composition do not reveal how the
components at a level interact to produce the
patterns of organization
Interactions
Interactions
Interactions
Interactions
Levels of Organization
• Organization often emerges from simple
interactions of components as we saw with
fall webworms and as see saw with army
• Another meaning of Levels (i.e., levels of
organization) is the number, strength, and
kinds of interactions among components at a
level of composition
• Flocking Boids
Levels of Organization
Levels of Organization
Time Scale and Levels of Composition
Time Scale and Interactions
Complexity and Levels of Organization
• Complex systems are not limited to interactions among
components at only one level of composition
• Oxytocin is a peptide hormone
– It is involved in the process of birth and nursing in
mammals
– It is also involved in social behavior
• E.g., attachment, social recognition and aggression
• Vasopressin is also a peptide hormone
– Regulates kidney function
– It is also involved in social behavior
• E.g., aggression and pair-bond formation, and mediating anxiety
Complexity and Levels of Organization
Scientific Perspectives and Level of
Organization
Scientific Perspectives × Levels of
Organization
Causation
• Our ordinary meaning of causation is a
relationship between events: cause and effect
such that certain conditions that bring about
certain effects
• Causation in this sense is proximate, which
means that the conditions bringing about an
effect are near their effects in space, time, and
typically at the same level of organization
Aristotle
• He thought of causes as reasons or factors explaining
the objects and processes that exist in the world.
• For Aristotle there were four basic causes
1. Material Cause: The material of which a thing is made.
2. Efficient Cause: The conditions that combine to produce
an effect from acause.
3. Formal Cause: The shape, configuration or type of thing
something is.
4. Final Cause: The purpose or end of a thing or process.
Aristotelian Causation
Aristotelian Causation
• Works well for explaining artifacts that we
build
• Does not work well for explaining biological
systems from an evolutionary-developmental
view
• No corresponding sense formal cause in
biological systems
• No corresponding sense of final cause in
biological systems
A Reinterpretation of Aristotle’s four
causes
1.
2.
3.
4.
Composition corresponds closely to Aristotle’s notion of material cause. It is the
components, entities and processes that compose a system at some level of
organization
Proximate Cause corresponds closely to Aristotle’s notion of efficient cause.
These are the causal conditions specified in mechanisms for how things work,
such as the firing of a neuron, or hormonal factors that modulate reproduction
and maternal care of young
Organization is somewhat related to one aspect of Aristotle’s notion of formal
cause, namely the idea of configuration. Organization is configuration or pattern
of interactions that emerge from the interactions among components of a
systems
Function: The notion of function is the biggest departure from Aristotle’s system.
In biology and psychology we replace Aristotle’s notion
a.
b.
System function: This is the role of a component in a system. For example, a function of a
neuron is to modulate action potentials. A function the heart is to circulate blood
Evolutionary adaptive function: This is the role of a component in the survival and
reproduction of a system in a larger ecosystem or environment. Typically, adaptive functions
are ascribed to components and characteristic of individuals, but they may apply to entities
at other levels of organization such as groups, ecosystems, and species
Army Ants
• Army ants are an interesting example of the complex
organization that illustrate different kinds of causes
operating during development.
• T. C. Schneirla studied army ants throughout the 1940s
• Army ants are nomadic foraging social insects. Unlike
many other social ants, wasps and bees they do not
build permanent nests (video1, video2)
• One of the more remarkable aspects of army ant social
behavior is that individual development is highly
coupled with social behavior and individual
development drives social behavior.
Cycles of Behavior
• Army ants exhibit daily or diurnal cycles of functional activity.
• Functional activity includes daytime foraging (when light, temperature and
humidity are best), thermoregulation and climate control in the bivouac
• These functional cycles are largely under external control of the daily light
cycle, temperature and humidity conditions. These are external
Zeitgebers.
• They go through Nomadic and Statary phases of colony behavior that are
tightly coupled with development of offspring
• Interestingly, these cycles are not driven by external Zeitgebers but
emerge from the individual interactions of workers, new workers and
pupae.
• Colony Functional Cycle refers to the functions performed by the colony
such as foraging and incubation, care and feeding of the next generation
on a daily basis
• Brood Cycle is a much longer cycle lasting more than 30 days during which
the colony produces a new brood
Cycles of Behavior
Brood Cycle
How are these cycle produced?
•
•
•
•
External Zeitgebers? No
Internal biological clocks? No
The queen running the colony? No
Local interactions among old works, new workers, and
larva? Yes
– Newly eclosed brood (first spike above threshold) of
workers increase the activity levels of old workers due to
chemical signals they (new workers release)
– Developing larvae (the second more gradual rise) release
larva pheromones and nutritive secretions that the
workers ingest, which increases the worker’s activity and
spreads throughout the colony
Army Ants and Causation
1. Composition: queen, old workers, new workers, larva,
pupa, chemicals for signaling
2. Proximate Cause: licking and grooming, physical
contact, release of chemical signals
3. Organization: colony functional cycle, brood cycle,
raiding patterns, bivouac formation
4. Function:
a. System function: forage for food, care for larva, pupa,
and queen
b. Evolutionary adaptive function: produce members of the
colony and, in particular, reproductive males and females
to found new colonies