Systems Thinking and System Dynamics

Systems (with s) Thinking and System (without s) Dynamics are two terms which are often used interchangeably, but in fact they are different. What is their relation to each other?

Systems thinking is a rather general term used by people in systems studies to denote a belief in systems as a holistic approach, in distinction to a reductionist approach of looking at parts of the system. The catch phrase is that the system is more than the sum of its parts. In particular, the interactions of the parts may cause the emergence of interesting behavior totally unanticipated when we only look at the parts individually.
The key is in the interactions.

Peter Senge made this approach popular in his book "The Fifth Discipline -The Art & Practice of The Learning Organization ",

where he also presented a set of intuitive patterns, called archetypes, of systemic behavior.
Examples of such patterns include "the harder you push, the harder the system pushes back", "the tragedy of the commons",and "eroding goals". These patterns can be understood intuitively without resorting to numeric equations or simulations.

Hence, it is correct to regard systems thinking as some sort of qualitative reasoning, which can be refined to a System Dynamics model.

Senge formulated 11 Laws of the Fifth Discipline as follows:

1. - today's problems come from yesterday's "solutions"
2. - the harder you push, the harder the system pushes back
3. - behavior grows better before it grows worse
4. - the easy way out usually leads back in
5. - the cure can be worse than the disease
6. - faster is slower
7. - cause and effect are not closely related in time and space
8. - small changes can produce big results --but the areas of highest leverage are often the least obvious
9. - you can have your cake and eat it too --but not at once
10. - dividing an elephant in half does not produce two small elephants
11. - there is no blame

One interesting application of Systems Thinking is the analysis of terrorism as an escalation process, see e.g here and "Systems Thinking Look at Terrorism."
The pattern here is "the chicken and egg" pattern, which comes first, the chicken or the egg, the violence or the retaliation?

The term System Dynamics was coined by Jay Forrester of the MIT Sloan School of Management, in his work on Industrial Dynamics, Urban Dynamics and World Dynamics, to describe a modeling methodology for the behavior of complex systems over time. The variables are called stocks(items with inventory levels) and flows (rates of change). The variables are connected using arcs which can form feedback loops.

Mathematically, a System Dynamics model is equivalent to a set of (algebraic, differential and integral) equations, whose solutions describe the time evolution of the system.
These models, particularly negative feedback loops made us acutely aware of growth limits, as put in the
"Limits to Growth" manifesto of the Club of Rome.

Systems Dynamics is again different from dynamical systems, which are systems studied in complexity science, for their limiting behavior such as cycles and other attractors, stability and chaotic behavior. Systems Dynamics is a methodology, dynamical system is a kind of mathematical object. Both however can give rise to nonlinear properties.

Summary of Systems Thinking(ST) and System Dynamics(SD):

• both agree that things are interconnected (in Buddhism: dependent origination)
  
• both use Causal Loop Diagrams to depict systems, SD also refines the model numerically using stocks and flows
  
• ST is qualitative, SD can be numerical which allow simulation and "what-if" experimentation
  
• both have applications in corporate and public management, environment, social sciences, decision making, and nonlinear dynamics
  
• ST has explicit delays, SD has delays within stocks
  
• SD stocks has memory to accumulate past events
  
• both use archetypes or patterns
  
• SD stresses learning by doing via experimentation of the system parameters
  
• both allow emergent properties
  
• both allow chaos to happen
  
• both ST and SD: the difficulty lies in developing models and validating them

References:

• John J. Shibley: "A Primer on Systems Thinking & Organizational Learning"
  
• Systems Thinking
  
• Road Maps: A Guide To Learning System Dynamics
  
• theWayofSystems
  
• MIT OpenCourseWare: System Dynamics for Business Policy
  
• MIT OpenCourseWare: Applications of System Dynamics
  
• systems-thinking.de: Systems thinking links displayed as a network

Software (from Wikipedia)

• Consideo free software combination of different methods, e.g. system dynamics
  
• AnyLogic non-free software, supports system dynamics, agent based and discrete event modeling
  
• Simile non-free System Dynamics software with object-based concepts
  
• Vensim non-free zero-cost software for educational and personal use
  
• MapSys non-free, zero-cost system thinking software
  
• Powersim Commercial system dynamics software
  
• Powersim Solutions internet-based simulation delivery software platform
  
• Forio non-free web-based system dynamics software with a zero cost version
  
• Stella and iThink Commercial system dynamics software