IV Classroom Modes: Improving the Model

The goal of classroom activity is to improve the student model by identifying issues and repairing them, and by adding to the model.

The Improving the Model mode contains two Level III Modeling Phases, Evaluate Model and Modify Model. These two phases can appear as large, distinct segments of classroom activity, or they can rapidly alternate. In Example 1, this alternation is very rapid--a student evaluates and immediately suggests a modification.

A student drawing has a diagram of lungs with a red arrow leading from the lungs to a heart. Another red arrow leads down to a capillary bed in the toe and a blue arrow leads from the capillary bed back to the heart. Inside the lungs is the word "Air." An annotation leads to the lungs and says, "A filter allows air in not liquids."

Example 1 

Students in a 7th grade class had generated different models of human circulation. One model was a single loop model of circulation where blood ran from the heart to body tissues to the lungs and back to the heart (Figure 1). (This is the correct model for fish--using gills--so it is not a bad first guess.) The teacher led the class in evaluating this model in whole class discussion, and it became clear that some students were concerned that it showed an artery returning to the heart, which was a violation of a rule they had learned. One student said that she liked this model, but thought perhaps it needed improvement (evaluation), “I don't know how, but I think either a vein or an artery might branch off and go to (the lungs) first" (modification). This suggested modification constitutes an incremental step toward the target model, because it begins to move away from a single-loop system and suggests a separate branch that involves the lungs. (For another part of this classroom discussion, see Example 1 under Model Competition mode.)

Figure 1: Single-loop model of human circulation being evaluated by students, who identified issues in it and suggested possible ways to repair them.


Although individual students may evaluate and propose modifications in rapid succession, as in Example 1, there are instances where a teacher may want to structure this mode so that the general focus of classroom discussion is clearly on one modeling phase and then on the other. This can form larger classroom-wide cycles of evaluation and modification. A number of strategies we have observed teachers use are on the Level III pages for the individual modeling phases Evaluate Model and Modify Model. Below are some examples where the teacher explicitly asked for evaluation and then for modification.

Three examples of teacher-led cycles of evaluation and modification

Example 2

Another teacher, Teacher R, using the same curriculum as in the previous example, asked the students to draw their ideas about how the blood carries oxygen and glucose to the big toe. Students drew just one red line from the heart to the toe, representing an artery. The teacher then asked the students, “What happens to the blood when it gets to the big toe’s cells?” They discussed possible options; for instance, it bathes the cells, it stays there, it returns to the heart. The students decided that there must be little vessels, capillaries (where the blue and red lines meet at the bottom of the figure in Example 1). The teacher also asked how the blood goes from the toe back to the heart. The students concluded that the blood carries waste back to the heart, so it must travel through another kind of blood vessel (a vein, the long blue vessel in Example 1). The teacher's Requests for Modification also fostered Model Evaluation by implying gaps in the students' current model.  

Example 3  

A cartoon diagram of a human head has been annotated by a student to show a tube leading from nose down through the throat, and another tube leading from the mouth down through the throat. The two tubes do not connect.In a lesson in which students construct a model of the throat, often students will suggest some variation of a two-tube model with one tube going from nose to the lungs and another tube going from mouth to stomach. At that point, a teacher could ask, “Does anyone see any possible problems?” Or, “Can you breathe and swallow at the same time?”  This will usually lead students to evaluate the model and identify one or more issues. At that point, the teacher can ask how the model could be modified to repair the issue. This process can be repeated with as many cycles as necessary to develop a good model.

Example 4

When constructing a model of the throat, after discarding a two-tube model, students may arrive at a one-tube model that handles both air and food (M3, M4). At this point, the teacher could ask, “How does food know which tube to go down?” In one class, the teacher suggested that there must be “something” in the throat that helps it do only one thing at a time. This was an invitation for students to suggest a modification. Impressively, they came up with ideas for a structure very like the epiglottis (M5).
The same cartoon head as in the previous figure has been annotated differently. A tube from the nose joins a tube from the mouth. Particles are shown in the lower part of the tube below the mouth. The mouth has been annotated, "Saliva enzymes"The cartoon head from the previous images has been further notated. Now the single tube from the nose and mouth reaches down into the chest and then divides into two tubes, one labelled "to lungs" and the other labelled "to stomach".The same cartoon head is annotated as in the previous image, but now has a small bump just above where the tube splits. This bump extends into the throat and is labeled "Epiglottis."


Supporting and Contributing Strategies

The Improving the Model Classroom Mode contains smaller Modeling Phases:

III. Evaluate Model
III. Modify Model

Several Creative Reasoning strategies that are apt to be helpful are grouped together under:

II. Support Evaluation
II. Support Modification

There are many Visualization strategies that may be helpful. Among them:

I. Depictive Gestures
I. Scientific Drawings
I. Mental Simulations



A discussion of this classroom mode in the context of a classroom example is in Core of this Approach.

Some of the background for this mode and how it fits into the larger framework is in the Level IV section of the Educator's Tour.

For more discussion on the theoretical underpinnings of this part of the framework, see the Introduction to the Full Theory page.


Articles, Papers and Websites

More in-depth discussion is found in the following paper by the team:

Large scale scientific modeling practices (Nunez-Oviedo & Clement, 2019)