II Creative Reasoning Processes to Support Model Modification

These are ways to support student reasoning while they are modifying a model.

Adding or Subtracting Model Elements
Extreme Case Reasoning to Support Modification
Using Analogies to Support Modification

There are many Level I strategies that can help support these processes; a few are listed at the bottom of this page.


Adding or subtracting model elements

Request that students add or subtract model elements to a model undergoing modification.

A humorous outline drawing of a human head and upper torso has been annotated by a student. A tube has been drawn leading down from the nose. The back of the mouth opens into this tube. The tube extends down into the chest and then divides into two tubes, one labeled "to lungs" and the other labeled "to stomach". There are other labels: “Nose,” “Saliva enzymes,” “Teeth Mouth Tongue,” and “Throat.” There is nothing in the throat to direct substances to one tube or the other; anything could go to either the lungs or the stomach.Example 1

In a class where students were learning about the structure of the throat, after much discussion, the students had agreed on a model where the nose and mouth connect in a single tube, and then farther down that tube branches into two tubes, one to the lungs and another to the stomach. However, their model was still missing an important element the teacher wanted them to consider. The students had already agreed that food does not go into the lungs. Now the teacher asked, “What is going to prevent the food from going down to your lungs?” The students speculated that there had to be a muscle, or something like a sliding door or a trap door. The teacher’s question can be interpreted as a request for a new model element, and the students interpreted it that way, immediately giving a variety of suggestions for what that new element might be like.

Hand drawing of what is essentially a single lung with a suggestion of two lobes. It has mostly hollow space inside with a hole at the top for air to get in and another hole at the bottom, presumably for the air to get out.Example 2

A small group had drawn a model of the lungs that had a hole at the bottom for air to get to the body.

T: You have this [hole in lung] that ll the air can sink out of; what do you want to do about that?

Example 3

Students were constructing a model of charge flow and resistance within a circuit.

T: Can anybody think of a way to make the model better, to account for our finding that not all bulbs light with the same brightness?

A professionally drawn diagram of a human chest shows the bronchial tube and lungs. One of the lungs has a cutaway to show the inside. Inside are air tubes and alveoli, which fill the lungs with tissue and structure.  This is unlike the early student drawings, which showed the lungs as mostly hollow.Example 4

In this example, the teacher supplies a new element for the students’ mostly hollow models of the lungs (as in Example 2).

T: Lungs are not hollow; they’re filled with tissue and little air cavities.

The teacher then showed a slide of the structure of a lung. This supplied the idea that lungs are not hollow, but students still had a lot of elements to supply to reach the target model. 

This was actually part of a long model-improvement cycle; see the sequence of images on our home page for part of it.

Image from Energy in the Human Body: A Middle School Life Science Curriculum, by Rea-Ramirez, Nunez-Oviedo, and Clement (2004).


Extreme Case Reasoning to Support Modification

Engage students in extreme case reasoning to to trigger ideas for improving the model.

Discussion is about the effects of setting an extremely high or low value for some variable in the system to trigger ideas for improving the model.

Example 5

An example comes from a high school class in which students were discussing sources of resistance to current flow in a circuit with a battery and a bulb. Students agreed that the light bulb offered resistance but most had the impression that the wires did not. (Although the resistance of the wires is small, it is not zero.) The instructor asked whether, if the wires extended to a bulb on the moon and back, they would offer resistance--and many of the student thought that in that case they would. This helped them see that there could be some very tiny resistance from the wires in a normal circuit.


Using Analogies to Support Modification

Six classroom examples.

Example 6: Teacher-requested analogy

T: You’ve already seen one analogy about water flowing through pipes. Is there some other analogy you can think of that would explain why this filament would have higher resistance than that filament?

Example 7: Student-provided analogies

This drawing is the same as in Example 1 above, with a  humorous drawing of a human head with a tube from nose and mouth dividing in two to go to the lungs and stomach. Here the drawing is in color, and we see a blue eye and blue earring. The throat structures are drawn in red. This diagram now has a new structure added by the class--a small bump just above where the tube splits. This bump extends into the throat and is labeled "Epiglottis." In Example 1, when the students answered the teacher’s question about the structure of the throat, they did so with analogies.

T: What is going to prevent the food from going down to your lungs?

S1: The thingy-

T: Describe what it looks like?

S2: A muscle.

S3: A sliding door.

T: Maybe a sliding door- any other possibilities?

S4: A one-way door; a trap door.

In the teacher’s last utterance, she repeated a student analogy and asked for other possibilities, which resulted in another student analogy. This one was more useful for helping the students invent the new model element that was needed, which eventually appeared in their model. (This element can be seen in the figure labelled "Epiglottis," though that label was not supplied until later. This is not the final model--the labels on the tubes have yet to be switched. The tube to the lungs will branch off in front and be the tube that gets closed off by the “trap door.”)

Examples 8-11 are actually a single excerpt from a classroom discussion that alternates between teacher and student-provided analogies about how leg veins help blood return to the heart. This is the same class in which the throat lesson (Examples 1 and 7) had occurred sometime before. In that lesson, students had come up with the idea of a one-way door to keep food from going into the lungs.

Example 8: Teacher-provided analogy

T: What might help blood in the veins move from your toe back up to your heart? Just think. If you wanted to get toothpaste out, you squeeze it. What could squeeze your veins?

S: Muscles around them.

T: Muscles around them, right? And in fact, it’s the skeletal muscles that are sort of helping to squeeze us.

Example 9: Student-provided analogy (continuation of Example 8)

T: But is blood a solid pasty liquid?

S: No.

T: No, it’s not like toothpaste, is it? So your blood vessels are going to need something [else]--it’s a design in your veins. What do you think it would be?

(Student flaps her hands together and apart)

T: What’s this? (mimics gesture)

S: Like fingers, brush things in your veins.

Example 10: Teacher-provided analogy (continuation of Example 9)

T: When you eat food, and you want to make sure it doesn’t go into your lungs, how does your body help you not do that?

S: It makes a little flap (flaps his hand)

T: It makes the little flap close. So what do you think the veins might have?

S: Flaps.

Example 11: Student-provided analogy (continuation of Example 10)

S: Flaps.

S: Like a lobster trap.

The sequence above is a great example of teacher-student co-construction, where both the teacher and the students are contributing ideas. In fact the teacher later adopted the student's flapping gesture to show how the valves in the veins work.

                                               Teacher is looking at her class, has her elbows high and out to the side. Her fingertips are touching and her forearms create a shallow V. Her hands and fingers represent a closed valve.The teacher has bent her hands upward from the wrist, as though the valve has opened. Her hands now form an upside down V with a gap of a few inches between her fingertips.


Supporting and Contributing Strategies

Extreme Case Reasoning and Using Analogies can involve mental animation. There are a number of visualization strategies teachers can use to help with this. See:

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

Different Participation Strategies may be needed at this point in the lesson.

I. Participation Strategies


Articles and Websites

More in-depth discussion and more student examples are found in the following papers by our team:

Generating, evaluating, and modifying scientific models using projected computer simulations (Price & Clement, 2014)

Documenting the use of expert scientific reasoning processes by high school physics students (Stephens & Clement, 2010)