Lego bricks, students, target concept, Karen, analogy, NRC, R.B. Thiele, R. Duit, National Academy Press, science education, mental model, gelatin mold, Athens, Georgia, relevant features, Upper Saddle River, NJ, Josiah Meigs, cell analogies, cell parts, animal cell, human cells, an animal cell, National Science Education Standards, Shawn Glynn, Resources Glynn, College of Education, University of Georgia, Pearson Education
Ideas and techniques to enhance your science teaching
The Teaching-With-Analogies Model Build conceptual bridges with mental models
By Shawn Glynn
Teachers often use analogies and are unaware of it--they are using them automatically. Whenever they begin an explanation with "It's just like...," "It's similar to...," or "Think of it this way...," they are using an analogy to explain a concept to their students. An analogy is a similarity between concepts. Analogies can help students build conceptual bridges between what is familiar and what is new. Often, new concepts represent complex, hard-to-visualize systems with interacting parts (e.g., a cell, an ecosystem, photosynthesis). Analogies can serve as early "mental models" that students can use to form limited but meaningful understandings of complex concepts. Analogies can play an important role in helping students construct their own knowledge, a process that is encouraged in the Standards and consistent with a constructivist view of learning. As students' develop cognitively and learn more science, they will evolve beyond these simple analogies, adopting more sophisticated and powerful mental models. The following case is a composite based on Observational Studies
of exemplary teachers who have used the Teaching-With-Analogies Model (Glynn 2004; Glynn, Duit, and Thiele 1995) to help their students connect new ideas with
their relevant prior knowledge
. The model has been validated in formal experiments and classroom settings in which the strategic use of analogies has been found to increase students' learning and interest. What We're Made Of "What are we made of?" asks Juan. He and many other students in Karen Park's fifth-grade class recently saw a Superman movie and were arguing about whether the Man of Steel was really made of steel. The students quickly agreed that Superman wasn't made of steel, but that got them thinking about what real people are made of. Karen welcomes the question, considering it a teaching opportunity,
even though it occurs before the students will actually have a formal lesson on the cell. "Well, Juan, boys are made of snakes and snails and puppy dog tails; and girls are made of sugar and spice and everything nice!" says Karen with a smile, having a bit of fun а la Mother Goose. After her students' laughter subsides, Karen explains, "But really, you're made up of cells--in fact, all animals and plants are made up of cells. The cells in you are alive, just as you are. Every part of us is made up of cells, but we can't see them because cells are usually so small you need a magnifying glass or a microscope to see them. Let me show you what cells are like." Karen quickly gets a box of Lego bricks from her supply cabinet. Next, she dramatically spills the unassembled bricks on her desk where all her students can see them. "What are these little bricks and what can you do with them?" asks Karen. "They're Legos!" many of the students cry. "You can build things with them," Juan adds, and the other students nod enthusiastically. "Exactly," Karen replies, and she quickly builds a little person from the bricks and holds it above her head so all her students can see it. "Lego bricks are like cells," Karen explains, pointing to the little Lego person. "Lego bricks get put together to make bigger things. Likewise,
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cells get put together to make bigger things--things like people, dogs, cats, oak trees, or rose bushes-- these living things are made up of cells--lots and lots of tiny cells." To ensure that her students understand her, she asks them to name other animals and plants, and after each one is named, Karen proclaims "Yes, that's made of cells!" "Listen carefully, because this is very important," Karen says. "Lego bricks are like your cells, but they're not the same as your cells. How are Lego bricks and your cells different?" "Lego bricks are bigger than my cells because I can see the Lego bricks," said Juan. "That's right, the cells that you're made of are much smaller than Lego bricks!" replied Karen. "And Lego bricks are not alive but my cells are," said another student, Tonja. "Right again," Karen agreed, "your cells are alive." Tonja beamed back a smile. "When you compare two things that are similar in some ways but different in other ways, you are making an analogy," explains Karen. "I made an analogy between Lego bricks and cells. Making an analogy helps you to understand something new by comparing it to something you already understand." Finally, Karen draws some conclusions for her students about cells. "What's important to remember," she says, "is that we're made up of cells, the cells are alive, and a microscope is needed to see our cells because they're so tiny. If we think about ourselves as being made up of cells, it will help us understand how our bodies work, grow, get sick, and get well again.
You'll be learning a lot more about cells in the future because the more you know about cells, the more you'll know about life." Steps to Follow While most students will be familiar with an analog concept such as a Lego, there may be some who are not. Therefore, it is important to ensure that all students are familiar with the analog concept in order for it to be effective. Teachers should also explain to students what an analogy is and ask students to draw their own analogies to further their understanding. Teachers should keep in mind that an analogy is a double-edged sword. If used carefully, it can make complicated concepts meaningful to students; if used carelessly, however, it can cause students to form misconceptions (e.g., human cells snap together like Lego bricks). Misconceptions can occur in places where the analogy breaks down, so teachers should "head students off at the pass" by pointing out these places to students. The steps in the Teaching-WithAnalogies Model help teachers use analogies systematically and effectively: 1. Introduce the target concept, the cell, to students. 2. Remind students of what they know of the analog concept, a Lego. 3. Identify relevant features of the cell and a Lego. 4. Connect (map) the similar features of the cell and a Lego. 5. Indicate where the analogy between the cell and a Lego breaks down. 6. Draw conclusions about the cell.
One implication of the Teaching-With-Analogies Model is that teachers should try to select analogs that share many similar features with the target concept. In general, the more features shared, the better the analogy. Another implication is that teachers should verify that students have not formed misconceptions. One way to do this is to ask focused questions about features that are not shared between the analog and the target concept. Another way to do this is to ask students to generate their own analogies and indicate where the analogies break down. It is important to remember that an analogy serves as an early "mental model" that connects prior knowledge with new knowledge when teaching a complex concept. The analogy paves the way for the expansion of the concept in an instructional unit and the teaching of a more sophisticated mental model. Analogy-based Activities Now that Karen has laid the conceptual foundation for cells, she can expand the concept by showing her students cell diagrams, photos, and videos and describing the different kinds of cells. Her students learn that the cells in their bones are different from the cells in their heart or brain and that their bodies are made up of about 200 different types of cells, all working together. As they progress through a unit on cell structure and function, students eventually learn that each cell must make the molecules it needs to survive, grow, and multiply--and that each cell is made up of parts, including organelles, with important functions.
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As the students learn about the parts of cells and the function of these parts, Karen uses analogy-based activities such as making an "edible cell" from gelatin, fruits, and candies (see Internet Resources). She again relies on the Teaching-With-Analogies Model, following its steps: 1. Introduce the target concept, the animal cell and its parts, to students. 2. Remind students of what they know of the analog concept, the gelatin mold and its parts. 3. Identify relevant features of the cell and the gelatin mold. 4. Connect (map) the similar features of the cell and the gelatin mold: e.g., nucleus (plum), mitochondria (raisins), lysosomes (M&M candies), endoplasmic reticulum (gummy worms), ribosomes (candy sprinkles), Golgi complex (folded hard candy ribbon), cytoplasm (gelatin), and cell membrane
(gelatin surface). 5. Indicate where the analogy between the cell and the gelatin mold breaks down (e.g., the cell is alive and tiny, with parts that only superficially resemble the fruits and candies in the gelatin mold). 6. Draw conclusions about the cell (e.g., cells are the building block
s of organisms and all the functions that sustain life occur within a single cell). Depending upon the amount of time available, Karen either has the students make their cells at home or she asks them to bring in ingredients for an in-class, collaborative project. Cakes, cookies, pizzas, and sandwiches also can be made into edible
cells, with the parts that represent the organelles labeled. Karen uses a rubric that assigns points to the edible cells, based on the correct inclusion of organelles. Make sure to check for student allergies before having students eat the assignment-- and enjoy the snack outside of the science lab. Elaborate Analogies When the students are ready for an advanced lesson, Karen crafts a more elaborate analogy: one that compares an animal cell, its parts, and the functions of those parts to a factory that makes products such as toys, automobiles, or television sets. She again follows the six steps in the TeachingWith-Analogies Model. She explains to her students: "Think about an animal cell and how its parts work together (Step 1).You might think of an animal cell as a tiny factory that uses materials, does jobs, and makes things. Just the way that different people in a factory do different jobs, different parts of the cell do different jobs (Step 2)." Next, she helps her students identify and map (by writing on the board) some similarities between cell parts and factory parts (Step 3). For example, the nucleus is like the factory control center, the ribosomes that make proteins are like the factory production machines, and the mitochondria are like the factory power generators (Step 4). Additional comparisons between factory parts and cell parts can be found online (see Internet Resources). Karen also warns her students "This factory-cell analogy, like all analogies, breaks down in a lot of plac-
es (Step 5). For example, the factory has doors and windows, but the cell doesn't. The cell has an outer layer, a membrane, that lets some things in and keeps other things out." Finally, Karen encourages her students to draw conclusions about the cell (Step 6) and make their own cell analogies. In response, Juan says, "A cell is like our city. The cell has parts that work together and so does our city. In our city, the mayor controls things, and in the cell this is done by the nucleus." Juan's cell-city analogy reminds Karen of a NASA educational website that explains how to increase students' understanding of the cell and its parts by making a cell-city mobile (see Internet Resources). Making a cell-city mobile would be a good class project to combine science and art. Making Them Meaningful The Teaching-With-Analogies Model can serve as a guide for teachers when constructing analogies to help explain key concepts in science. If analogies are already in the books the students are using, then teachers can use the model to ensure that the analogies are effective. Teachers should tailor analogies and analogy-based activities to fit students' knowledge and experiences to ensure that the analogies are familiar and meaningful. Also, students should be encouraged to construct their own analogies, keeping in mind the limitations of analogies. Constructing their own analogies helps students to take an active role in their learning and builds conceptual bridges between what they already know and what they are setting out to learn.
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Shawn Glynn ([email protected]
edu) is a Josiah Meigs Distinguished Teaching Professor in the College of Education, University of Georgia, Athens, Georgia. Resources Glynn, S.M. 2004. Connect concepts with questions and analogies. In Cases in middle and secondary Science Education
, eds. T.R. Koballa and D.J. Tippins,136142. Upper Saddle River, NJ: Pearson Education
. Glynn, S.M., R. Duit, and R.B. Thiele. 1995. Teaching science with analogies: A strategy for constructing
Connecting to the Standards This article relates to the following National Science Education Standards (NRC 1996): Content Standards Grades 58 Standard C: Life Science · Structure and function in living systems knowledge. In Learning science in the schools: Research reforming practice, eds. S.M. Glynn and R. Duit,
247273. Mahwah, NJ
: Erlbaum. National Research Council
(NRC). 1996. National science education standards. Washington DC
: National Academy Press. Internet Comparing a Cell to a Factory www.sciencenetlinks.com/pdfs/ cellsystem_actsheet.pdf Cell City Mobile www.nasaexplores.com/show_58_ teacher_st.php?id=040830142039 Jello 3-D Animal Cell Craft www.enchantedlearning.com/ subjects/animals/cell/jello.
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