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March 18, 2004

On Teaching Chandralekha Singh


Chandralekha Singh

Are outstanding teachers born that way?

“Anybody can become a good teacher by thinking about the learning process, and how they can help the students,” insists Chandralekha Singh, senior lecturer at Pitt’s Department of Physics and Astronomy.

“Teaching is an art to some extent, but I think any instructor can develop the necessary skills. I think you can cultivate teaching.” Singh knows about good teaching: She has won several teaching awards including the 2002 Chancellor’s Distinguished Award for Teaching Excellence and the 2000 College of Arts and Sciences Bellet Teaching Excellence Award.

A native of India, Singh earned a B.S. with honors in physics at the Indian Institute of Technology in Kharagpur and a Ph.D. in physics from the University of California, Santa Barbara, one of the top physics programs in the United States.

This term, Singh is teaching an introductory physics course with 80 students, an intermediate course for majors and engineering students with 50 students and a pre-service teaching course with four physics majors interested in becoming teachers themselves.

“I had some very good teachers and I’ve always been fascinated with good teaching,” Singh says. “I think particularly in physics, success depends on students’ beliefs about what physics is. If students are thinking that physics is just a bunch of facts and formulas that need to be memorized with no relation to the real world, or that it’s just writing down what the teacher says because the instructor is really smart, or if it means giving up if they can’t solve a problem in the first five minutes, then I think students won’t have the desire or the motivation or the right attitude to learn physics,” she says.

But instructors who employ building-block learning techniques, use real world examples and offer encouragement in the face of initial student failures can win over a class of any size, Singh maintains.

Good teaching starts on the first day of the term, Singh says. “As instructors, we have to make it clear to the students in the first class: These are our goals. So students know very well what I expect to do, and what I expect them to be able to do by the end of the course.”

In Singh’s case, that means making it clear that her courses are not about spouting back facts at exam time. “I’ll say, ‘This course is about conceptual understanding and being able to relate the concepts of physics to everyday life, being able to explain why things work in a certain way and being able to articulate that.’ And it’s important, as the course goes along, to give specific examples to reinforce the kinds of things I expect them to be able to do.”

Drawing on Benjamin Bloom’s 1956 essay on the taxonomy of educational objectives, which categorizes competence into stages of understanding — knowledge, comprehension, application, analysis, synthesis, evaluation — Singh says that many teachers fall short of the ultimate goal of real understanding.

“I can say: ‘I want you to memorize: Acceleration is the rate of change in velocity with time.’ That gives them some knowledge,” she says. “But if I ask them questions like: ‘If the car was moving in the east direction at 60 miles an hour, and then it started moving 30 miles an hour north and that change happened over a period of seven seconds, what is the average acceleration of the car in magnitude and direction,’ will they be able to do that?”

Students need to learn to use the knowledge, a process she calls knowledge organization. “By usable knowledge I mean that it doesn’t get shampooed out right after the final exam; it’s something you’ve made your own, something that will be with you forever. That’s what learning is, and as instructors we need to be there to ‘scaffold’ that learning.”

That scaffolding process first requires evaluating how prepared the students are, she says. Singh gives ungraded “pre-tests” to measure her students’ preparation levels early on in a course, but she says that measurement is an ongoing process.

“You continue to find out where they are by talking to students individually and seeing how they do on exams and assignments, where you can often tell what kinds of difficulties they have as well as what level their current knowledge is,” she says. “Over time, you get a very good feel for what you need to emphasize.”

It is critical, she says, for instructors to put themselves in their students’ shoes.

“If I were trying to explain a physics principle to my kids or to my mother or to a non-physics major — thinking about this helps me work through what kinds of things I really need to cover and how I should build it up so students can actually understand it.”

The traditional lecture format with a passive audience doesn’t cut it, she insists. “That model is not going to work. First of all, half of what I say is just bouncing off them, and the other half is going into some notebook, and it’s lost there,” she says.

“Learning anything requires effort and so students have to be actively engaged in the learning process, in reconstructing, organizing and extending their knowledge.”

Singh will begin a class lecturing on a physics concept, but quickly introduce a related question, usually in multiple choice format so she can poll the students.

She’ll say, “‘Okay, why don’t you talk to your neighbors about this question and see whether they agree with you or not.’” She stresses that they can change their mind at any time. “Because they have to articulate these things to their peers, it gives an opportunity to organize their knowledge. I really believe that there is a social aspect of learning that you can exploit.”

Following the students’ discussion, she polls the class about which multiple-choice answer each student thinks is correct.

“This helps in several ways: It benefits all students. First of all, they are all alert, knowing that they will be asked to give an answer; second, they are trying to synthesize the information they have learned, because I asked them to apply the principle; third, they need to be able to articulate to fellow students why they came up with the answer they did.”

Also, if a significant percentage of the class gets the wrong answer, it is a signal to explain the principle further, she adds.

She asks students who answered the question correctly to explain their reasoning to the rest of the class. “Since they know they had the correct answer, they’re oftentimes willing to offer their reasoning.”

Usually, she will refine their explanations and add other examples of applications of the same principle.

“In physics there are not that many major principles. But those principles are applied in so many diverse, real-world situations. If I give just one example of conservation of energy, for example, and I expect students to apply it to a range of contexts, I’m expecting too much of them,” she says. “So, in my homework, in my class discussion, in my feedback, in the questions I ask in class, I continue to provide different contexts. I want them to learn, for example, that when a ballerina puts her arms close to herself to spin faster it is the same principle as what makes a neutron star that is collapsing move faster. I want them to make those connections.”

Physics textbooks, which typically are linear, often impede such connections. “Chapter 1 is about displacement and velocity; chapter 2 is about net forces; chapter 3 is about energy. The books often don’t make the connection between these things, and they are all related to each other. Professors make a big mistake if they assume students are making the connections on their own.”

Students also will come to a physics course steeped in misconceptions. “We are all, from the day we’re born, trying to make sense of the world and even if things are not explained to us, we continue to interpret them in terms we already know,” she says.

One common misconception is that if an object is moving at a constant velocity in a straight line, there must be a force acting on that object. “But physics says, ‘No, there is no net force acting on that object. Only if the velocity changes, then there must be a force acting on the object because forces change velocity. Force is proportional to the rate of change in velocity,” she says.

“The point is if these misconceptions are not elicited, dissected, confronted, resolved — if they don’t learn what was wrong in their thinking — then on the exam, all the misconceptions show up,” Singh says.

To combat that danger, she breaks down assignments so that students are asked to predict an answer, with no penalty for an incorrect prediction, before they actually solve a problem by demonstration.

“If I tell them a three-volt battery does not provide a fixed amount of current even though it has a fixed amount of voltage, just saying that does not really make students know what I’m talking about,” she maintains.

Students may predict a consistent amount of current from the battery. “Then you ask, ‘What happens if the resistance in the circuit is one ohm verses two ohms? Why is the current different?’ They make predictions and then have to reconcile what they found later with what they had thought. Their conceptions have been challenged, they see things are not fitting, and that motivates them to think about resolving the problem. They also have the freedom to guess wrong without penalty, which acts as a stimulus to learning.”

On the other hand, instructors also can take advantage of what students do know.

“There are things we can build on,” Singh says. “For example, many students already know something about velocity; they may not have the correct notion about it, but through their experience they’re partly correct. When you drive in a car and hit your brakes, you lunge forward. When the car is at rest and you hit the accelerator, you move back.”

Voila: acceleration. “Acceleration is what you feel when you move [faster], while if you’re moving at a constant velocity you will not feel anything.

“If you think about the way we learn, we’re always trying to connect new knowledge to our prior knowledge,” she says. “If there is good connection between what we already know and what you’re telling me, I’m very much likely to extend my knowledge, organize my knowledge and remember it.”

—Peter Hart

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