Subject: 12/10/04 WSJ Article on How Schoolchildren Learn

Posted by Gallaher Ed on 12/19/2004
In Reply To:12/10/04 WSJ Article on How Schoolchildren Learn Posted by Elisabeth Roberts on 12/17/2004

Message:

Agreed, a great deal of learning and clarification evolve during, and as a result of the modeling process, beginning with fuzzy brainstorming sessions among the participants.

I agree entirely; there is no ONE correct model! Various structures may evolve to solve, or to illustrate slightly different problems. Even for the same problem, individuals may have honest differences of opinion re the model structure, assumptions, parameter values, etc. Such discussions highlight some of the most important advantages of the systems thinking approach.

However, it is a stretch to say there are as many 'correct' models as there are modelers. This is akin to saying there are as many 'correct' answers to an algebra problem as there are students working on the problem.

It can be enlightening to use stock-and-flow diagrams, or causal-loop diagrams, to expose feedback relationships to the light of day. (e.g.
consider an ongoing discussion of salmon population dynamics, hydroelectric power generation, economics, and politics with h.s. students in any one of a number of relevant classes).

Consider a stock [salmon population], with appropriate birth rates and death rates.

Growing populations typically (must!) exhibit S-shaped growth; they simply cannot, and will not, grow infinitely.

This -cannot- occur with the simple structure described above. There is NO WAY this structure can exhibit S-shaped dynamic behavior. There MUST be another loop (e.g. decreased per capita food due to population density) that serves to SHIFT the loop dominance from a reinforcing loop (exponential
growth) to a balancing loop (stable population; carrying capacity).

Lest I be misinterpreted: I am NOT suggesting that everyone needs an M.S.
degree from MIT or WPI to be judged competent. I am suggesting that as teachers, (or better, learning coaches) we have a responsibility to NOT present our audiences with incorrect materials.

Lest I be misinterpreted (again): If the 'learning coach' is working WITH the students, and the question is raised, 'How does this relationship lead to S-shaped growth?', then EVERYONE gets to consider the underlying structure, dynamics, etc. THIS IS GOOD, even if the intermediate structure is less than perfect.

However, if an incorrect structure is introduced as the explanation for S-shaped growth, and is accepted by the audience without further examination, then -EVERYONE- leaves the table with a long-term misunderstanding of the real structure, and the real dynamics.

I humbly suggest: We already have too many (well-meaning [we hope]) economists, politicians, fisherpeople, and ecologists working under the burden of various critical misconceptions.

Let's enable our students to do a better job!

> our responsibility to systems learners is to make clear the level of
> confidence we can have in a particular diagram or model's accuracy to
> depict the actual system "out there."

EXACTLY my point!

Ed Gallaher