Using Causal Loop Diagrams to depict feedback loops

Kim Kastens, Lamont-Doherty Earth Observatory

Courtney Sheckler, Temple University

Thomas F. Shipley, Temple University

Alexandra Davatzes, Temple University

Author Profile
Initial Publication Date: June 25, 2025

Summary

Causal loop diagrams (CLDs) are a form of graphic model used for depicting systems – especially systems involving feedback loops – by means of arrows and text nodes. This student activity provides introductory practice in the use of CLD's for positive and negative feedback loops. For each question in the main activity, students are provided with a narrative description of a feedback loop accompanied by a partially-completed CLD. Their task is to complete the CLD and the narrative. Challenge level ramps up from the beginning to end of the activity: from completed examples, through highly-scaffolded instances, to slightly-scaffolded instances. Two versions of the activity are provided: one with only two nodes per loop and one with three nodes. This activity is intended as preparation for activities in which students must think deeply about one or more loop-driven systems relevant to the course content. The activity prepares them to use CLDs to externalize their mental models of feedback loops, for example in brainstorming with peers about an intervention to solve a problem. We also provide an optional warm-up activity in which students reason about single links one at a time before tackling multi-link CLDs.

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Context

Audience

This activity is designed for undergraduates (beginning majors or non-majors at any level) in any course that teaches about one or more feedback loops. The instances come from a variety of science and non-science domains, so as to emphasize that feedback loops have explanatory power across many domains. The activity can be used as provided, or the instructional approach could also be modified to use instances that are tailored to the instructor's own course content.

Skills and concepts that students must have mastered

Students should have basic familiarity with the concepts of feedback loops, and with the difference between positive (aka "reinforcing") and negative (aka "balancing") feedback loops.

How the activity is situated in the course

The activity is suited for students to do on their own as homework, with the intent that they will then come to class with a shared graphic language that they can use in subsequent assignments, either in-class collaborative activities or independent projects or papers. Alternatively, this could be done as a small-group activity in class, prior to seguing into an activity in which students have to create their own CLDs.

Goals

Content/concepts goals for this activity

  • Students will be able to understand causal loop models that others have created for simple feedback loop systems.
  • Students will be able to create causal loop models to depict their own understanding of a simple feedback loop system.
  • Students will be prepared to use causal loop models in a collaborative activity with peers, for example to compare and contrast working hypotheses about how a system works or would work under different circumstances.

Higher order thinking skills goals for this activity

  • Causal reasoning: Students will strengthen their ability to think carefully about the circumstances under which a change in something causes a change in something else, and what the nature of that change is likely to be.
  • Model-making: Students will strengthen their understanding of the nature of scientific models, recognizing that diagrammatic models are a representation of the model-maker's understanding of a system that exists (or might exist in the future or might have existed in the past).

Skills goals for this activity

  • Make and interpret causal loop diagrams.

Description and Teaching Materials

First, students read a short narrative that describes a positive feedback loop and examine an accompanying causal loop diagram. Then they do the same for a negative loop. Importantly, for these examples, the narratives explain why the loop is positive or negative.

Next, they read narratives describing other feedback loops. For these loops, the CLD is not complete, and the narrative does not explain whether the loop is positive or negative. The students' task is to fill in the blanks in the CLD and the narrative, including identifying and explaining whether the loop is positive or negative. As students progress through the activity, less and less information is provided, until on the final question they have to fill in all the elements of the CLD.

We also provide an optional warm-up activity. For each of the items in the warm-up activity, students see two nodes connected by a straight line. They have to put an arrowhead onto one end of the line to indicate the direction of causal influence from one node to the other, and label the arrow with an "S" or "O" to indicate whether a change in the upstream node causes a change in the Same or Opposite direction in the downstream node.

Teaching Notes and Tips

About terminology: This activity uses "positive (+)" and "negative (-)" as terms and symbols to describe self-reinforcing and self-limiting loops because these terms are in widespread usage in U.S. college science departments. You could substitute "reinforcing (R)" and "balancing (B)" if those terms are in use in your department. We use "S" for "same" links and "O" for "opposite" as the labels on individual links in CLDs. We recommend against using + and - signs for individual links because students tend to expect that + means that the downstream node will increase and - means that the downstream node will decrease.

Use this activity as a building block: For "Teaching the Earth," causal loop diagrams are a tool to enable clearer thinking and communication about natural or human-natural systems that involve feedback loops, not an end unto themselves. Thus, we encourage instructors to use this activity as a precursor or foundation for a more demanding activity that requires students to think deeply, either on their own or in collaboration with peers, about an Earth system that is important in the content domain of the course. Some suggestions:

  • Find the feedback loop in popular media: Students find a description of a feedback loop in an article from popular media, depict the loop in a CLD and accompanying narrative, and describe the impact of the loop on the larger system within which the loop is embedded.
  • Feedback Loops in the Field: Students identify two feedback loops during a local field trip, name the loop, describe or diagram the loop, and determine if the loop is negative or positive.
  • Intervening in a Feedback Loop [LINK coming soon]: Students write an essay on ways to disrupt positive feedback loops (vicious cycles) through Meadows' (1999) framework for ways to intervene in a system. 

For online use: The 2-node version was used in an asynchronous online course; students were allowed to print the page, write on it, and submit via a photo, or download the Word file and add responses directly on the page and upload, or students could make a pdf and draw on it with an Ipad.

Metacognitive reflection: If you emphasize metacognition in your teaching, we include (in the two-node version) an optional "Think about your thinking" question that prompts students to compare the advantages and disadvantages of narrative versus graphical/diagrammatic representation.

Make your own: if you would like to make your own version of this activity with content specialized for your course, you might appreciate the video How to Make Excellent Causal Loop Diagrams, provided in Resources.


Assessment

  • One way to determine if students have met the goals of this activity is to check their answers. An answer key is provided. However, there may be correct answers that do not exactly match the answer key, so look carefully at the logic. For example: Amount of praise --S--> Employee Happiness is on the answer key, but Amount of praise --O--> Employee unhappiness would also be an acceptable answer.
  • You can also wait and see how effectively they use CLDs in supporting their arguments in a follow-on assignment.

References and Resources