1. Levels of Organization, Complexity, and Causation PSC 120 Jeff Schank

2. Outline Levels of Organization – Composition – Interactions Complex Systems Complexity and Levels of Organization Scientific Perspectives and Organization Causation – Aristotle’s Four Causes – A Reformulation of Aristotle’s Four Causes Agent-Based Simulation

3. First an Example Fall Webworms

4. 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

5. Levels of Composition

7. Interactions Levels of composition do not reveal how the components at a level interact to produce the patterns of organization

8. Levels of Organization Organization often emerges from simple interactions of components as we saw with fall webworms 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

9. Levels of Organization

11. Complex Systems

12. Complexity and Levels of Organization

13. Scientific Perspectives and Level of Organization

14. Scientific Perspectives × Levels of Organization

15. 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

16. 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.

17. Aristotelian Causation

18. 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

19. A Reinterpretation of Aristotle’s four causes 1.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 2.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 3.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 4.Function: The notion of function is the biggest departure from Aristotle’s system. In biology and psychology we replace Aristotle’s notion a.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 b.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

20. Emergence and Causation With our modern notion of Aristotelian causation, we can characterize biological and other complex systems in terms of the first three causes

21. Another view of Emergence

22. Flocks of Starlings

23. Schools of Fish

24. Herds of Mammals

26. Agent-Based Simulation