Dr. Rebecca Ambrose, Helping Our Students Build a Meaningful Understanding of Geometry
ROUNDING UP: SEASON 3 | EPISODE 8
As a field, mathematics education has come a long way over the past few years in describing the ways students come to understand number, quantity, place value, and even fractions. But when it comes to geometry, particularly concepts involving shape, it’s often less clear how student thinking develops. Today, we’re talking with Dr. Rebecca Ambrose about ways we can help our students build a meaningful understanding of geometry.
BIOGRAPHIES
Rebecca Ambrose researches how children solve mathematics problems and works with teachers to apply what she has learned about the informal strategies children employ to differentiate and improve instruction in math. She is currently a professor at the University of California, Davis in the School of Education.
RESOURCES
Geometry Resources Curated by Dr. Ambrose
TRANSCRIPT
Mike Wallus: As a field, mathematics education has come a long way over the past few years in describing the ways that students come to understand number, place value, and even fractions. But when it comes to geometry, especially concepts involving shape, it's often less clear how student thinking develops. Today, we're talking with Dr. Rebecca Ambrose about ways we can help our students build a meaningful understanding of geometry.
Well, welcome to the podcast, Rebecca. Thank you so much for joining us today.
Rebecca Ambrose: It's nice to be here. I appreciate the invitation.
Mike: So, I'd like to start by asking: What led you to focus your work on the ways that students build a meaningful understanding of geometry, particularly shape?
Rebecca: So, I taught middle school math for 10 years. And the first seven years were in coed classrooms. And I was always struck by especially the girls who were actually very successful in math, but they would tell me, “I like you, Ms. Ambrose, but I don't like math. I'm not going to continue to pursue it.” And I found that troubling, and I also found it troubling that they were not as involved in class discussion. And I went for three years and taught at an all-girls school so I could see what difference it made. And we did have more student voice in those classrooms, but I still had some very successful students who told me the same thing. So, I was really concerned that we were doing something wrong and that led me to graduate school with a focus on gender issues in math education. And I had the blessing of studying with Elizabeth Fennema, who was really the pioneer in studying gender issues in math education.
And as I started studying with her, I learned that the one area that females tended to underperform males on aptitude tests—not achievement tests, but aptitude tests—was in the area of spatial reasoning. And you'll remember those are the tests, or items that you may have had where you have one view of a shape and then you have a choice of four other views, and you have to choose the one that is the same shape from a different view. And those particular tasks we see consistent gender differences on. I became convinced it was because we didn't give kids enough opportunity to engage in that kind of activity at school. You either had some strengths there or not, and because of the play activity of boys, that may be why some of them are more successful at that than others.
And then the other thing that informed that was when I was teaching middle school, and I did do a few spatial activities, kids would emerge with talents that I was unaware of. So, I remember in particular this [student,] Stacy, who was an eighth-grader who was kind of a good worker and was able to learn along with the rest of the class, but she didn't stand out as particularly interested or gifted in mathematics. And yet, when we started doing these spatial tasks, and I pulled out my spatial puzzles, she was all over it. And she was doing things much more quickly than I could. And I said, “Stacy, wow.” She said, “Oh, I love this stuff, and I do it at home.” And she wasn't the kind of kid to ever draw attention to herself, but when I saw, “Oh, this is a side of Stacy that I didn't know about, and it is very pertinent to mathematics. And she needs to know what doorways could be open to her that would employ these skills that she has and also to help her shine in front of her classmates.” So, that made me really curious about what we could do to provide kids with more opportunities like that little piece that I gave her and her classmates back in the day. So, that's what led me to look at geometry thinking. And the more that I have had my opportunities to dabble with teachers and kids, people have a real appetite for it. There are always a couple of people who go, “Ooh.” But many more who are just so eager to do something in addition to number that we can call mathematics.
Mike: You know, I'm thinking about our conversation before we set up and started to record the formal podcast today. And during that conversation you asked me a question that involved kites, and I'm wondering if you might ask that question again for our listeners.
Rebecca: I'm going to invite you to do a mental challenge. And the way you think about it might be quite revealing to how you engage in both geometric and spatial reasoning. So, I invite you to picture in your mind's eye a kite and then to describe to me what you're seeing.
Mike: So, I see two equilateral triangles that are joined at their bases—although as I say the word “bases,” I realize that could also lead to some follow-up questions. And then I see one wooden line that bisects those two triangles from top to bottom and another wooden line that bisects them along what I would call their bases.
Rebecca: OK, I'm trying to imagine with you. So, you have two equilateral triangles that—a different way of saying it might be they share a side?
Mike: They do share a side. Yes.
Rebecca: OK. And then tell me again about these wooden parts.
Mike: So, when I think about the kite, I imagine that there is a point at the top of the kite and a point at the bottom of the kite. And there's a wooden piece that runs from the point at the top down to the point at the bottom. And it cuts right through the middle. So, essentially, if you were thinking about the two triangles forming something that looked like a diamond, there would be a line that cut right from the top to the bottom point.
Rebecca: OK.
Mike: And then, likewise, there would be another wooden piece running from the point on one side to the point on the other side. So essentially, the triangles would be cut in half, but then there would also be a piece of wood that would essentially separate each triangle from the other along the two sides that they shared.
Rebecca: OK. One thing that I noticed was you used a lot of mathematical ideas, and we don't always see that in children. And I hope that the listeners engaged in that activity themselves and maybe even stopped for a moment to sort of picture it before they started trying to process what you said so that they would just kind of play with this challenge of taking what you're seeing in your mind's eye and trying to articulate in words what that looks like. And that's a whole mathematical task in and of itself. And the way that you engaged in it was from a fairly high level of mathematics.
And so, one of the things that I hope that task sort of illustrates is how a.) geometry involves these images that we have. And that we are often having to develop that concept image, this way of imagining it in our visual domain, in our brain. And almost everybody has it. And some people call it “the mind's eye.” Three percent of the population apparently don't have it—but the fact that 97 percent do suggests for teachers that they can depend on almost every child being able to at least close their eyes and picture that kite. I was strategic in choosing the kite rather than asking you to picture a rectangle or a hexagon or something like that because the kite is a mathematical idea that some mathematicians talk about, but it's also this real-world thing that we have some experiences with.
And so, one of the things that that particular exercise does is highlight how we have these prototypes, these single images that we associate with particular words. And that's our starting point for instruction with children, for helping them to build up their mathematical ideas about these shapes. Having a mental image and then describing the mental image is where we put language to these math ideas. And the prototypes can be very helpful, but sometimes, especially for young children, when they believe that a triangle is an equilateral triangle that's sitting on, you know, the horizontal—one side is basically its base, the word that you used—they've got that mental picture. But that is not associated with any other triangles. So, if something looks more or less like that prototype, they'll say, “Yeah, that's a triangle.” But when we start showing them some things that are very different from that, but that mathematicians would call triangles, they're not always successful at recognizing those as triangles. And then if we also show them something that has curved sides or a jagged side but has that nice 60-degree angle on the top, they'll say, “Oh yeah, that's close enough to my prototype that we'll call that a triangle.”
So, part of what we are doing when we are engaging kids in these conversations is helping them to attend to the precision that mathematicians always use. And that's one of our standards. And as I've done more work with talking to kids about these geometric shapes, I realize it's about helping them to be very clear about when they are referring to something, what it is they're referring to. So, I listen very carefully to, “Are they saying ‘this’ and ‘that’ and pointing to something?” That communicates their idea, but it would be more precise as like, I have to ask you to repeat what you were telling me so that I knew exactly what you were talking about. And in this domain, where we don't have access to a picture to point to, we have to be more precise. And that's part of this geometric learning that we're trying to advance.
Mike: So, this is bringing a lot of questions for me. The first one that I want to unpack is, you talked about the idea that when we're accessing the mind's eye, there's potentially a prototype of a shape that we see in our mind's eye. Tell me more about what you mean when you say “a prototype.”
Rebecca: The way that that word is used more generally, as often when people are designing something, they build a prototype. So, it's sort of the iconic image that goes with a particular idea.
Mike: You're making me think about when I was teaching kindergarten and first grade, we had colored pattern blocks that we use quite often. And often when we talked about triangles, what the students would describe or what I believed was the prototype in their mind's eye really matched up with that. So, they saw the green equilateral triangle. And when we said trapezoid, it looked like the red trapezoid, right? And so, what you're making me think about is the extent to which having a prototype is useful, but if you only have one prototype, it might also be limiting.
Rebecca: Exactly. And when we're talking to a 3- or a 4-year-old, and we're pointing to something and saying, “That's a triangle,” they don't know what aspect of it makes it a triangle. So, does it have to be green? Does it have to be that particular size? So, we’ll both understand each other when we're talking about that pattern block. But when we're looking at something that's much different, they may not know what aspect of it is making me call it a triangle” And they may experience a lot of dissonance if I'm telling them that—I'm trying to think of a non-equilateral triangle that we might all, “Oh, well, let’s”—and I'm thinking of 3-D shapes, like an ice cream cone. Well, that's got a triangular-ish shape, but it's not a triangle. But if we can imagine that sort of is isosceles triangle with two long sides and a shorter side, if I start calling that a triangle or if I show a child that kind of isosceles triangle and I say, “Oh, what's that?” And they say, “I don't know.”
So, we have to help them come to terms with that dissonance that's going to come from me calling something a triangle that they're not familiar with calling a triangle. And sadly, that moment of dissonance from which Piaget tells us learning occurs, doesn't happen enough in the elementary school classroom. Kids are often given equilateral triangles or maybe a right triangle. But they're not often seeing that unusual triangle that I described. So, they're not bumping into that dissonance that'll help them to work through, “Well, what makes something a triangle? What counts and what doesn't count?” And that's where the geometry part comes in that goes beyond just spatial visualization and using your mind's eye, but actually applying these properties and figuring out when do they apply and when do they not apply.
Mike: I think this is probably a good place to shift and ask you: What do we know as a field about how students' ideas about shape initially emerge and how they mature over time?
Rebecca: Well, that's an interesting question because we have our theory about how they would develop under the excellent teaching conditions, and we haven't had very many opportunities to confirm that theory because geometry is so overlooked in the elementary school classroom. So, I'm going to theorize about how they develop based on my own experience and my reading of the literature on very specific examples of trying to teach kids about squares and rectangles. Or, in my case, trying to see how they describe three-dimensional shapes that they may have built from polydrons. So, their thinking tends to start at a very visual level. And like in the kite example, they might say, “It looks like a diamond”—and you actually said that at one point—but not go farther from there.
So, you decomposed your kite, and you decomposed it a lot. You said it has two equilateral triangles and then it has those—mathematicians would call [them] diagonals. So, you were skipping several levels in doing that. So, I'll give you the intermediate levels using that kite example. So, one thing a child might say is that “I'm seeing two short sides and two long sides.” So, in that case, they're starting to decompose the kite into component parts. And as we help them to learn about those component parts, they might say, “Oh, it's got a couple of different angles.” And again, that's a different thing to pay attention to. That's a component part that would be the beginning of them doing what Battista called spatial structuring. Michael Battista built on the van Hiele levels to try to capture this theory about how kids’ thinking might develop. So, attention to component parts is the first place that we see them making some advances.
And then the next is if they're able to talk about relationships between those component parts. So, in the case of the kite, they might say, “Oh, the two short sides are equal to each other”—so, there's a relationship there—“and they're connected to each other at the top.” And I think you said something about that. “And then the long sides are also connected to each other.” And that's looking at how the sides are related to the other sides is where the component parts start getting to become a new part. So, it's like decomposing and recomposing, which is part of all of mathematics.
And then the last stage is when they're able to put the shapes themselves into the hierarchy that we have. So, for example, in the kite case, they might say, “It's got four sides, so it's a quadrilateral. But it's not a parallelogram because none of the four sides are parallel to each other.” So now I'm not just looking at component parts and their relations, but I'm using those relations to think about the definition of that shape. So, I would never expect a kid to be able to tell me, “Oh yeah, a kite is a quadrilateral that is not a parallelogram,” and then tell me about the angles and tell me about the sides without a lot of experience describing shapes.
Mike: There are a few things that are popping out for me when I'm listening to you talk about this. One of them is the real importance of language and attempting to use language to build a meaningful description or to make sense of shape. The other piece that it really makes me think about is the prototypes, as you described them, are a useful starting place. They’re something to build on.
But there's real importance in showing a wide variety of shapes or even “almost-shapes.” I can imagine a triangle that is a triangle in every respect except for the fact that it's not a closed shape. Maybe there's an opening or a triangle that has wavy sides that are connected at three points. Or an obtuse triangle. Being able to see multiple examples and nonexamples feels like a really important part of helping kids actually find the language but also get to the essence of, “What is a triangle?” Tell me if I'm on point or off base when I'm thinking about that, Rebecca.
Rebecca: You are right on target. And in fact, Clements and Sarama wrote a piece in the NCTM Teaching Children Mathematics in about 2000 where they describe their study that found exactly what you said. And they make a recommendation that kids do have opportunities to see all kinds of examples. And one way that that can happen is if they're using dynamic geometry software. So, for example, Polypad, I was just playing with it, and you can create a three-sided figure and then drag around one of the points and see all these different triangles. And the class could have a discussion about, “Are all of these triangles? Well, that looks like a weird triangle. I've never seen that before.” And today I was just playing around with the idea of having kids create a favorite triangle in Polypad and then make copies of it and compose new shapes out of their favorite triangle.
What I like about that task, and I think can be a design principle for a teacher who wants to play around with these ideas and get creative with them, is to give kids opportunities to use their creativity in making new kinds of shapes and having a sense of ownership over those creations. And then using those creations as a topic of conversation for other kids. So, they have to treat their classmates as contributors to their mathematics learning, and they're all getting an opportunity to have kind of an aesthetic experience. I think that's the beauty of geometry. It's using a different part of our brain. Thomas West talks about Seeing What Others Cannot See, and he describes people like Einstein and others who really solved problems visually. They didn't use numbers. They used pictures. And Ian Robertson talks about Opening the Mind's Eye. So, his work is more focused on how we all could benefit from being able to visualize things. And actually, our fallback might be to engage our mind's eye instead of always wanting to talk [chuckles] about things.
That brings us back to this language idea. And I think language is very important. But maybe we need to stretch it to communication. I want to engage kids in sharing with me what they notice and what they see, but it may be embodied as much as it is verbal. So, we might use our arms and our elbow to discuss angle. And well, we'll put words to it. We're also then experiencing it in our body and showing it to each other in a different way than [...] just the words and the pictures on the paper. So, people are just beginning to explore this idea of gesture. But I have seen, I worked with a teacher who was working with first graders and they were—you say, “Show us a right angle,” and they would show it to us on their body.
Mike: Wow. I mean, this is so far from the way that I initially understood my job when I was teaching geometry, which was: I was going to teach the definition, and kids were going to remember that definition and look at the prototypical shape and say, “That's a triangle” or “That's a square.” Even this last bit that you were talking about really flips that whole idea on its head, right? It makes me think that teaching the definitions before kids engage with shapes is actually having it backwards. How would you think about the way that kids come to make meaning about what defines any given shape? If you were to imagine a process for a teacher helping to build a sense of triangle-ness, talk about that if you wouldn't mind.
Rebecca: Well, so I'm going to draw on a 3-D example for this, and it's actually something that I worked with a teacher in a third grade classroom, and we had a lot of English language learners in this classroom. And we had been building polyhedra, which are just three-dimensional shapes using a tool called the polydrons. And our first activities, the kids had just made their own polyhedra and described them. So, we didn't tell them what a prism was. We didn't tell them what a pyramid was or a cube. Another shape they tend to build with those tools is something called an anti-prism, but we didn't introduce any of those terms to them. They were familiar with the terms triangle and square, and those are within the collection of tools they have to work with. But it was interesting to me that their experience with those words was so limited that they often confused those two. And I attributed it to all they'd had was maybe a few lessons every year where they were asked to identify, “Which of these are triangles?” They had never even spoken that word themselves. So, that's to have this classroom where you are hearing from the kids and getting them to communicate with each other and the teacher as much as possible. I think that's part of our mantra for everything.
But we took what they built. So, they had all built something, and it was a polyhedra. That was the thing we described. We said it has to be closed. So, we did provide them with that definition. You have to build a closed figure with these shapes, and it needs to be three-dimensional. It can't be flat. So, then we had this collection of shapes, and in this case, I was the arbiter. And I started with, “Oh wow, this is really cool. It's a pyramid.” And I just picked an example of a pyramid, and it was the triangular pyramid, made out of four equilateral triangles. And then I pulled another shape that they had built that was obviously not any—I think it was a cube. And I said, “Well, what do you think? Is this a pyramid?” And they'd said, “No, that's not a pyramid.” “OK, why isn't it?” And by the way, they did know something about pyramids. They'd heard the word before. And every time I do this with a class where I say, “OK, tell me, ‘What's a pyramid?’” They'll tell me that it's from Egypt. It's really big. So, they're drawing on the Egyptian pyramids that they're familiar with. Some of them might say a little something mathematical, but usually it's more about the pyramids they've seen maybe in movies or in school.
So, they're drawing on that concept image, right? But they don't have any kind of mathematical definition. They don't know the component parts of a pyramid. So, after we say that the cube is not a pyramid, and I say, “Well, why isn't it?,” they'll say, “because it doesn't have a pointy top.” So, we can see there that they're still drawing on the concept image that they have, which is valid and helpful in this case, but it's not real defined. So, we have attention to a component part. That's the first step we hope that they'll make. And we're still going to talk about which of these shapes are pyramids. So, we continued to bring in shapes, and they ended up with, it needed to have triangular sides. Because we had some things that had pointy tops, but it wasn't where triangles met. It would be an edge where there were two sloped sides that were meeting there. Let's see. If you can imagine, while I engage your mind's eye again, a prism, basically a triangular prism with two equilateral triangles on each end, and then rectangles that attach those two triangles.
Mike: I can see that.
Rebecca: OK. So, usually you see that sitting on a triangle, and we call the triangles the base. But if you tilt it so it's sitting on a rectangle, now you've got something that looks like a tent. And the kids will say that. “That looks like a tent.” “OK, yeah, that looks like a tent.” And so, that's giving us that Level 1 thinking: “What does it look like?” “What's the word that comes to mind?” And—but we've got those sloped sides, and so when they see that, some of them will call that the pointy top because we haven't defined pointy top.
Mike: Yes.
Rebecca: But when I give them the feedback, “Oh, you know what, that's not a pyramid.” Then the class started talking about, “Hmm, OK. What's different about that top versus this other top?” And so, then they came to, “Well, it has to be where triangles meet.” I could have introduced the word vertex at that time. I could have said, “Well, we call any place where sides meet a vertex.” That might be [a] helpful word for us today. But that's where the word comes from what they're doing, rather than me just arbitrarily saying, “Today I'm going to teach you about vertices. You need to know about vertices.” But we need a word for this place where the sides meet. So, I can introduce that word, and we can be more precise now in what we're talking about. So, the tent thing didn't have a vertex on top. It had an edge on top. So now we could be precise about that.
Mike: I want to go back, and I'm going to restate the thing that you said for people who are listening, because to me, it was huge. This whole idea of “the word comes from the things that they are doing or that they are saying.” Did I get that right?
Rebecca: Yeah, that the precise terminology grows out of the conversation you're having and helps people to be clear about what they're referring to. Because even if they're just pointing at it, that's helpful. And especially for students whose first language might not be English, then they at least have a reference. That's why it's so hard for me to be doing geometry with you just verbally. I don't even have a picture or a thing to refer to. But then when I say “vertex” and we're pointing to this thing, I have to try as much as I can to help them distinguish between, “This one is a vertex. This one is not a vertex.”
Mike: You brought up earlier supporting multilingual learners, particularly given the way that you just modeled what was a really rich back-and-forth conversation where children were making comparisons. They were using language that was very informal, and then the things that they were saying and doing led to introducing some of those more precise pieces of language. How does that look when you have a group of students who might have a diverse set of languages that they're speaking in the same classroom?
Rebecca: Well, when we do this in that environment, which is most of the time when I'm doing this, we do a lot of pair-share. And I like to let kids talk to the people that they communicate best with so that if you have two Spanish speakers, for example, they could speak in Spanish to each other. And ideally the classroom norms have been established so that that's OK. But that opportunity to hear it again from a peer helps them to process. And it slows things down. Like, often we're just going so fast that people get lost. And it may be a language thing; it may be a concept thing. So, whatever we can do to slow things down and let kids hear it repeatedly—because we know that that repeated input is very helpful—and from various different people.
So, what I'll often do, if I want everybody to have an opportunity to hear about the vertex, I'm going to invite the kids to retell what they understood from what I said. And then that gives me an opportunity to assess those individuals who are doing the retell and also gives the other students a chance to hear it again. It's OK for them to see or hear the kind of textbook explanation for vertex in their preferred language.
But again, only when the class has been kind of grappling with the idea, it's not the starting point. It emerges as needed in that heat of instruction. And you don't expect them to necessarily get it the first time around. That's why these building tasks or construction tasks can be done at different levels. So, we were talking about the different levels the learner might be at. Everybody can imagine a kite, and everybody could draw a kite. So, I'm sort of differentiating my instruction by giving this very open-ended task, and then I'm trying to tune into what am I seeing and hearing from the different individuals that can give me some insight into their geometrical reasoning at this point in time. But we're going to keep drawing things, and we're going to keep building things, and everybody's going to have their opportunity to advance. But it's not in unison.
Mike: A few things jumped out. One, as you were describing the experiences that you can give to students, particularly students who might have a diversity of languages in the same classroom, it strikes me that this is where nonverbal communication like gesturing or using a visual or using a physical model really comes in handy.
I think the other piece that I was reminded of as I was listening to you is, we have made some progress in suggesting that it's really important to listen to kids' mathematical thinking. And I often think that that's taken root, particularly as kids are doing things like adding or subtracting. And I think what you're reminding [me] is, that holds true when it comes to thinking about geometry or shape; that it's in listening to what kids are saying, that they're helping us understand, “What's next?” “Where do we introduce language?” “How can we have kids speaking to one another in a way that builds a set of ideas?”
I think the big takeaway for me is that sometimes geometry has kind of been treated like this separate entity in the world of elementary mathematics. And yet some of the principles that we find really important in things like number or operation, they still hold true.
Rebecca: Definitely, definitely. And again, as I said, when you are interested in getting to know your children, seeing who's got some gifts in this domain will allow you to uplift kids who might otherwise not have those opportunities to shine.
Mike: I think that's a great place to stop. Rebecca, thank you so much for joining us. It's been a pleasure talking to you.
Rebecca: This has really been fun. And I do want to mention one thing: that I have developed a list of various articles and resources. Most of them come from NCTM, and I can make that available to you so that people who are interested in learning more can get some more resources.
Mike: That's fantastic. We'll link those to our show notes. Thank you again very much for helping us make sense of this really important set of concepts.
Rebecca: You're welcome.
Mike: This podcast is brought to you by The Math Learning Center and the Maier Math Foundation, dedicated to inspiring and enabling all individuals to discover and develop their mathematical confidence and ability.