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| Aug 25 2009, 1:44 AM EDT (current) | chachabooth | 7 words added, 8 words deleted |
| Aug 21 2009, 3:35 AM EDT | chachabooth | 178 words added, 1 word deleted |
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Causal loops consist of variables (things that change over time, can take on different values) that are connected by arrows in a way that shows how one variable affects another. Causal loop diagrams are about showing how things are influencing each other. For example:
Now, weWe can drawlabel athe linearrows in order to show how these things related to each other. Anxiety at work has a “positive” influence – i.e. adds or changes in the same direction – toon the number of mistakes made at work. We can illustrate this by writing a + to the arrow from anxiety to number of mistakes. For the second pair of variablevariables we can see another waykind of relationship: Doing more relaxation exercises has a “negative” influence – i.e. subtracts or changes in the opposite direction – on the stress level. We can illustrate this by writing a - to the arrow from relaxation exercises to stress level.[1] A loop is formed as there is also a connection between the two variables the other way around: the number of mistakes in turn increases anxiety at work; if you are more stressed you do more relaxation exercises. This is of course a very simple example of a causal loop to make the point. We can use it to introduce the two principal kinds of causal loops: reinforcing loops and balancing loops.
In a reinforcing loop the causal relationship within the loop create exponential growth or collapse. For instance, the more anxious you are at work, the more mistakes you make and as you make more mistakes, you get even more anxious and so on. This is often also called a vicious cycle.[2] Any situation where action produces a result which promotes more of the same action is representative of a reinforcing loop. Some typical examples of reinforcing loops are: population growth and decline, snow balls running down the hill, wall street market crashes, violence sparking new violence, etc.
In a balancing loop the causal influences in the loop keep things in equilibrium. Any situation where one attempts to solve a problem or achieve a goal or objective is a balancing loop. Consider the above example, if you feel more stressed, you do more relaxation exercises, which brings your stress level down. Typical examples for balancing loops are when you develop a certain skill, build something, fix a problem. The figure below shows the basic form of a balancing loop. The desired state interacts with the current state – the discrepancy between the current and desired state creates a gap. The gap adds to the action and the action adds to the current state. The current state then subtracts from the gap. As the current state gets closer to the desired ones, the gap gets smaller so that it adds less to action. Once the current state equals the desired one, the gap is zero and does not add to action anymore.[3]
Systems contain many different reinforcing and balancing loops, all connected together with arrows. When you bring the different subsystems together, you will recognize the complexity of systems.
When drawing causal loop diagrams, a few things should be taken into account: [See Daniel H. Kim, Guidelines for Drawing Causal Loop Diagrams, in: The Systems Thinker <http://www.thesystemsthinker.com/tstgdlines2.html> (accessed 11 August 2009) as well as Kirkwood, Craig W., System Dynamics Methods: A Quick Introduction, 1998, p. 13f. < http://www.public.asu.edu/~kirkwood/sysdyn/SDIntro/ch-1.pdf> (accessed 13 August 2009)]
References:
Richardson, George P., Problems in Causal Loop Diagrams Revisited.<http://www.clexchange.org/ftp/documents/system-dynamics/SD1997-09ProblemsInCLDsRevi.pdf>(accessed 13 August 2009)
Stroh, Peter David, Identifying and Breaking Vicious Cycles, Applied Systems Thinking: 2006, p. 1. <http://www.appliedsystemsthinking.com/supporting_documents/Practice_ViciousCycles.pdf> accessed 9 August 2009)
Bellinger, Gene, Introduction to Systems Thinking, 2004. <www.systems-thinking.org/intst/int.htm> (accessed 10 August 2009)
"Causal Loop Diagrams" <http://www.thesystemsthinker.com/tstcld.html> (accessed 11 August 2009)
Kirkwood, Craig W., System Dynamics Methods: A Quick Introduction, 1998. < http://www.public.asu.edu/~kirkwood/sysdyn/SDIntro/ch-1.pdf> (accessed 13 August 2009)
Footnotes:
Adapted from "Causal Loop Diagrams" <http://www.thesystemsthinker.com/tstcld.html> (accessed 11 August 2009)
Now, weWe can drawlabel athe linearrows in order to show how these things related to each other. Anxiety at work has a “positive” influence – i.e. adds or changes in the same direction – toon the number of mistakes made at work. We can illustrate this by writing a + to the arrow from anxiety to number of mistakes. For the second pair of variablevariables we can see another waykind of relationship: Doing more relaxation exercises has a “negative” influence – i.e. subtracts or changes in the opposite direction – on the stress level. We can illustrate this by writing a - to the arrow from relaxation exercises to stress level.[1] A loop is formed as there is also a connection between the two variables the other way around: the number of mistakes in turn increases anxiety at work; if you are more stressed you do more relaxation exercises. This is of course a very simple example of a causal loop to make the point. We can use it to introduce the two principal kinds of causal loops: reinforcing loops and balancing loops.
In a reinforcing loop the causal relationship within the loop create exponential growth or collapse. For instance, the more anxious you are at work, the more mistakes you make and as you make more mistakes, you get even more anxious and so on. This is often also called a vicious cycle.[2] Any situation where action produces a result which promotes more of the same action is representative of a reinforcing loop. Some typical examples of reinforcing loops are: population growth and decline, snow balls running down the hill, wall street market crashes, violence sparking new violence, etc.
In a balancing loop the causal influences in the loop keep things in equilibrium. Any situation where one attempts to solve a problem or achieve a goal or objective is a balancing loop. Consider the above example, if you feel more stressed, you do more relaxation exercises, which brings your stress level down. Typical examples for balancing loops are when you develop a certain skill, build something, fix a problem. The figure below shows the basic form of a balancing loop. The desired state interacts with the current state – the discrepancy between the current and desired state creates a gap. The gap adds to the action and the action adds to the current state. The current state then subtracts from the gap. As the current state gets closer to the desired ones, the gap gets smaller so that it adds less to action. Once the current state equals the desired one, the gap is zero and does not add to action anymore.[3]
Taken from Bellinger, Gene, Introduction to Systems Thinking, 2004. <www.systems-thinking.org/intst/int.htm.> (accessed 10 August 2009)
Systems contain many different reinforcing and balancing loops, all connected together with arrows. When you bring the different subsystems together, you will recognize the complexity of systems.
When drawing causal loop diagrams, a few things should be taken into account: [See Daniel H. Kim, Guidelines for Drawing Causal Loop Diagrams, in: The Systems Thinker <http://www.thesystemsthinker.com/tstgdlines2.html> (accessed 11 August 2009) as well as Kirkwood, Craig W., System Dynamics Methods: A Quick Introduction, 1998, p. 13f. < http://www.public.asu.edu/~kirkwood/sysdyn/SDIntro/ch-1.pdf> (accessed 13 August 2009)]
- The elements of causal loop diagrams should be though of as variables, i.e. things that change over time.
- Use nouns when choosing the names of the variables in the causal loop. Avoid verbs and action phrases, because the action is conveyed in the loops arrows. For instance “costs” is much better than “increasing costs” as then a decrease in increasing costs would be confusing. The sign of the arrow – + or - – indicates whether costs increase or decrease in relation to the other variable in the loop.
- Use variables that represent quantities that can vary over time. It does not make sense to say that a state of mind increases or decreases. Happiness, satisfaction, anger, etc. can however increase or decrease depending on the other variable in the loop.
- Causal links are not simply a time sequence, but imply a direction of causation. A positive link from A to B does not mean that A occurs before B, but when A increases also B increases.
- Think of the possible unintended consequences as well as the expected outcomes for every course of action included in the diagram.
- Be aware of differences between short and long term consequences of actions. For instance, taking drugs brings short term satisfaction, but long term negative effects.
- If a link between two variables needs a lot of explaining this is an indication that you need to add intermediate elements that show more clearly what is happening.
- Keep the diagram as simple as possible. The purpose is not to describe every detail, but to show those aspects of the structure that lead to a pattern of behavior.
References:
Richardson, George P., Problems in Causal Loop Diagrams Revisited.<http://www.clexchange.org/ftp/documents/system-dynamics/SD1997-09ProblemsInCLDsRevi.pdf>(accessed 13 August 2009)
Stroh, Peter David, Identifying and Breaking Vicious Cycles, Applied Systems Thinking: 2006, p. 1. <http://www.appliedsystemsthinking.com/supporting_documents/Practice_ViciousCycles.pdf> accessed 9 August 2009)
Bellinger, Gene, Introduction to Systems Thinking, 2004. <www.systems-thinking.org/intst/int.htm> (accessed 10 August 2009)
"Causal Loop Diagrams" <http://www.thesystemsthinker.com/tstcld.html> (accessed 11 August 2009)
Kirkwood, Craig W., System Dynamics Methods: A Quick Introduction, 1998. < http://www.public.asu.edu/~kirkwood/sysdyn/SDIntro/ch-1.pdf> (accessed 13 August 2009)
Footnotes:
[1] Some models prefer to use the letter s (for positive influence – change in the same direction) and o (for negative influence – change in the opposite direction). According to Richardson, using these can lead to serious flaws in the causal loop diagrams, i.e. links not behaving as their symbols claim. He defines a + as follows “A adds to B, or, a change in A causes a change in B in the same direction” and a – “A subtracts from B, or, a change in A causes a change in B in the opposite direction”. Richardson, George P., Problems in Causal Loop Diagrams Revisited.<http://www.clexchange.org/ftp/documents/system-dynamics/SD1997-09ProblemsInCLDsRevi.pdf>(accessed 13 August 2009)
[2] Vicious cycles are a very accessible form of starting an introduction to systems thinking as most people have heard of vicious circles before. David Peter Stroh provides a number of examples for vicious circles (Stroh, Peter David, Identifying and Breaking Vicious Cycles, Applied Systems Thinking: 2006, p. 1. <http://www.appliedsystemsthinking.com/supporting_documents/Practice_ViciousCycles.pdf> accessed 9 August 2009)
- An epidemic accelerates in proportion to the to the number of people exposed, which in turn increases the likelihood that the epidemic will spread further.
- Downsizing is likely to reduce and executive’s ability to generate revenue (not just costs), which in turn decreases profits and increases pressure to downsize yet again.
- Acts of violence perpetrated by one party in a war stimulate acts of revenge by the other party, which in turn lead to violent retaliation by the first party and an ongoing escalation by both sides.
[3] See Bellinger, Gene, Introduction to Systems Thinking, 2004. <www.systems-thinking.org/intst/int.htm.> (accessed 10 August 2009)
