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Thinking in Diagrams

Chapter 4: Loops That Amplify, Loops That Correct

Drafted for Aryeh's edit.

For chapter 4: Loops That Amplify, Loops That Correct

Timing

Section titled “Timing”
  • Reading the chapter: about 11 minutes, its 1,594 words of prose at 150 words a minute. Not counted in those minutes: 4 figures, 1 pair, 3 understanding checks, the reading exercise and the exercises.
  • A session: 50 minutes, the exercises set for it. (estimate)
  • Afterwards: 60 minutes, the exercises set for then. (estimate)

Common misreadings

Section titled “Common misreadings”
  • A variable named as an action, an event or a change. The bad diagram’s three names, stock the shelves, order groceries and receive the delivery, fail the more test; in the lab, each such name raises a notice under Names, with every check passed. Three of the four choices in the understanding check under Variables are such names.
  • A balancing loop read as a good outcome, as + is read as good and − as bad. In the reading’s third question a balancing loop comes to dominate and overdose deaths rise; the choice overdose deaths fall, since a balancing loop corrects the problem is this misreading.
  • A loop’s kind judged by its purpose, or by most of its effects. The lab’s parity check reports a loop whose declared kind disagrees with its count of − effects, showing the count. Wrong choices in the understanding check under The parity rule (most of its effects are +) and in the reading’s first question (a call to 911 is made to bring overdose deaths down) read a loop this way.
  • A one-way chain where the situation closes a loop. Booth Sweeney and Sterman (2007) found open-loop, one-way causal thinking common among middle school students and teachers. In CL 01, a chain that never returns to its start leaves Close one loop unmet.
  • Delays left out, and a balancing loop expected to settle smoothly. The same study found explanations without time delays. A smooth rise, a choice in the understanding check about soup on a slow stove, is this expectation; in CL 03, Put a delay on building starts → housing stock stays unmet without one.

Exercises to set

Section titled “Exercises to set”

The session goes from one loop of each kind through a published diagram to two coupled loops; delays, a leverage point and the case come afterwards.

For a session

Afterwards

Sources

Section titled “Sources”