[MUSIC] Hello, this is Lee Jo Pina, and today, we will go through a tutorial on how to develop causal loop diagrams using Vensim. And I'd first like to acknowledge Professor Taki Gusam-Ng from the engineering school. We'll be using a model that he developed for a future health systems project workshop on complexity that took place in Baltimore in June 2014. Our session objectives today are to introduce you to using Vensim. And, the advantage of doing that is that it is a free software that everybody can have access to. Additionally we will demonstrate the development of a causal loop diagram in Vensim by using a public health example. First of all, in order for you to get access to Vensim, you just go to the website and you're able to download the PLE version for free. And this is handy because it can be used to build causal loop diagrams. Also stock and flow diagrams, which will be covered in another tutorial, and it also has basic modeling and analysis functions. If you are so inclined, there are more advanced versions available for purchase, and there is a discount for academic use. If you're interested to see into various features and compare them, you can go to this website that allows you to compare the various Vensim versions to see which one is best for your needs. Just a quick note that although today we will be using the Vensim software, there are also other software available to draw CLDs. For example, iThink, and CLDs or causal loop diagrams can also be drawn by hand, so you don't necessarily need a software to draw them. You might have seen this in the lecture, but this is a quick overview of the main causal loop diagram elements. So, to review them, first we have the variables which are the items of interest. These are linked together through causality and polarity, so we have to know the direction of the influence and we have to do that both through arrows and their signs. And the main feature of causal loop diagrams are feedback loops which can be reinforcing or balancing, and some of them are influenced by delays. To guide our tutorial today we will go through a simple scenario and we'll try to recreate the causal loop diagram that is at the bottom of the slide. There you will see three variables that are linked with arrows. And the description is illustrated in the four bullets. So, increases in technical quality leads to increases in the volume of services. So the better the quality of the services, the more people will come to get services at a particular facility, for example. However, as the volume of services increases over time, it might over burden the facility and therefore will erode at the technical quality. And that is denoted by the arrow with the double lines and the negative sign, and we'll go in greater detail on that in a second. On the left-hand side, we will see that there's an intervention, a reward that is introduced. And the reward is introduced to improve technical quality. The greater the reward, in theory, the greater the technical quality. Similarly, the greater the technical quality, the more facilities or individuals would be rewarded. And you will see that there are two loops that we will work to create. So to get started you'll first have to download the Vensim version from the Vensim website, as mentioned before. And then let's see about opening it on our computers. You will double click the Vensim logo on your desktop and you see that the Vensim workspace is opening. To open a new model you go to the top toolbar and the item that is on the furthest left is the new model icon. You click that and you get this pop-up window that tells you about model settings. This is not very relevant for causal loop diagrams. It will play a greater role in system dynamics or stock and flow diagrams, so for now we'll just press OK. So thinking back of the four main elements of the causal loop diagram, we'll try to recreate them now in our workspace. So the first element were the variables. So the corresponding first step is creating these new variables. So you click the Variable button and then go to the workspace area and click in the area where you would like to add the variables. So we have three variables. Let's start by adding the reward. We then add the technical quality. And finally we add the volume of services. You will see that you can move these variables with the little hand symbol. To delete a variable, let's say you made a mistake, you go to the top tool bar and click the delete button. And you're able to delete one or more variables that is no longer needed. In order to get that variable back or to go back a step, use the CTRL+Z button that is familiar from other programs as well. So, now that we've created, three variables, we want to also, display the relationships between them. And as you remember we do that by using arrows. So, we go to the top tool bar, click on the arrow button. And we begin to draw the arrows that illustrate the relationships that we proposed through words in the previous scenario. So, as mentioned earlier, technical quality causes a change in volume of services. And then a return volume of services causes a change in technical quality. Similarly reward was causing a change in technical quality, and vice versa. After we display these arrows, the next step is to add arrow properties. The arrow property that was most important is the polarity, and that denotes the direction of the change. So technical quality and volume of services we're moving in the same direction so they would need a plus sign. So in order to ad arrow properties we right click on the little knob that is at the center of each arrow. That is also used to move the arrows. Right clicking on that we can get another pop up menu. And here we will see the various features that we can add. The most important one is the polarity. And in this case we said it was a plus sign. We can also add delays in case that the effect of one variable on the other is delayed. We can change the color of the arrow. We can change the line style or thickness, and to make it perhaps easier, and something that I do regularly, is we can move the position of the polarity. For example, at the handle and at the outside. And then we click OK and we see that now we have a positive relationship between the two variables. So we do that quickly for the other ones. This one was special because we were saying that after some time, indicating a delay, the increase in volume of services actually erodes at the technical quality. Therefore the variables move in different directions and they would get a negative polarity. If we're inclined, we can also change the color of this arrow but that is only to highlight this relationship. It's not necessary. And as I mentioned, we've changed the position of the polarity to make it easier to read. The other two relationships were positive, so I'll just go very quickly through that. Increasing reward increases technical quality, and the quality increases, the greater the reward. So now we have completed adding arrow properties. The next step is labeling the loops. We have identified in this very simple diagram that there are two feedback loops. One was reinforcing, when there's an even number of plus signs or positive signs. And the other one was balancing where there's an uneven number of signs. So in order to label the loops, we use the Comment button that is on the top toolbar. So we click on the Comment button and then we click in the center of the loop usually and we get a new pop up menu. And this might seem like it has a lot of options but there are only a few things that we're interested in. In the comment box we will want to put an R to signify a reinforcing loop. We could've also used a plus sign, an image. Or there's this image of an avalanche that can also be used to signal reinforcing loops. And there's a variety of other options. Most are quite difficult to read, so I personally tend to use the R, because that also is less confusing, because you're using plus signs and minus signs to denote error properties. So we labeled the loop as reinforcing. The next thing that we would want to do is add a loop symbol from up here in the shapes sub menu. And we had the option to add clockwise loops and counterclockwise loops. These symbols help the person looking at the loop actually read it. It's for the benefit of your audience. This is more important in bigger causal loop diagrams, it's not so much important in our simple scenario, but we'll do it regardless. If I remember correctly this was a clockwise loop. Let's press OK. And as we'll see here, now we have a labeled reinforcing loop, and it's red in the clockwise direction. So, let's label the second one. This is a balancing loop. So add a B. And it is right in the counter clockwise direction. Alternatively as I mentioned earlier you could have used one of these symbols. And then we press OK. So you have the two loop labels here in the middle and you're able to move them by just using the same button as it becomes a hand. Now in more complicated causal loop diagrams you might also want to label not just whether it's balancing or reinforcing, but also if it has a particular name. So one that would make it, you know, if you have seven loops, perhaps you have a quality loop that you want readers to focus on. So if we want to do that, you can also add comments outside of your diagram. And then you would just add a descriptor. So for example, let's call this the quality loop, we could use the font options, for example, we could make it bold and italic, so that it looks distinct from the rest of the diagram. And therefore, in a much more complicated diagram the readers would know that this section is about quality. As you can see we have recreated the diagram that was first presented in the simple scenario. And this concludes our tutorial on drawing causal loop diagrams with Vensim. In summary, after opening the new model there were four simple steps and those were adding variables, linking them with arrows and denoting the properties of those arrows, and then identifying loops and labeling them. This is a causal loop diagram that can then serve to be a foundation for a stock and flow diagram, and that will be discussed in the tutorial on stock and flow diagrams. Now that we have completed the diagram, the next step is really the interpretation and analysis using the casual loop diagram. So the questions that one would want to ask is what does the feedback mean? Which feedback is desirable, which is undesirable? And also what are the other variables that would be useful to include? As I mentioned, this is a very simplified and perhaps oversimplified diagram but if you were to actually do this there would be many more variables that would be at play. The other question that one might want to ask is what factors could influence the delays that we observe? And finally, where and why would one intervene? Is the reward the only intervention that is applicable in this case, or are there other interventions that would be useful? In general, I wanted to also add some tips and tricks for drawing causal loop diagrams. Just reminders that all arrows need a polarity and all loops should be labeled. And it is convention to use curved lines, so using the little knob at each arrow to curve them is by convention a necessary element of causal loop diagrams. As they become more complicated, it is important to minimize crossed lines. And to not use circles, hexagons and other symbols. There are many options that Vensim gives you, but it's important to know which ones are useful and which ones are not necessary. Keeping our audience in mind, especially as causal loop diagrams become more complicated, it's important to remember that you don't have to put all the loops in one big diagram. You could have separate diagrams to really help the audience or whoever you're working with to understand the feedback and where that's coming from. And a final reminder, it's important to remember that this is an iterative process and that before a causal loop diagram is completed, there would be many versions that you would go through with your team, or your stakeholders. And that it's not just about the diagram, it's also the process that's also important in developing it. If you would like more information about developing causal loop diagrams, these are helpful resources that you might want to look at. John Sterman's book on Business Dynamics is a big textbook that has a lot of information, both about causal loop diagrams and also bowed stock and flow diagrams. Eric Pruyt's book is helpful to take you step by step through building models, including causal loop diagrams. Additionally, YouTube has a lot of free tutorials if you're interested in learning more. And the Vensim User Guide is also rich with resources. [MUSIC]
