Interactive Lectures: Roger Tobin

Professor and Chair, Department of Physics and Astronomy, School of Arts and Sciences, Tufts University

Physics professor Roger Tobin discusses his successful use of Peer Instruction, facilitated by clickers, to encourage student involvement during large physics lectures.

“Demonstrations don’t work unless you get the students to commit to an answer ahead of time. It’s a level of engagement with the material that you just don’t see if you just stand up there and do it.”

Roger Tobin shares his approach to teaching and reflects on lessons learned.

Teaching Context

Tobin teaches large introductory physics classes numbering anywhere from 80 to 180 students.  “The challenge in a large class,” he explains, “is to get a lot of students involved.  You can always invite questions but typically you only get a handful of vocal students then involved.”   Over the years he has experimented with different techniques to get a wider range of students engaged in class.

Two techniques that Tobin has used effectively are the Interactive Lecture Demonstration (ILD) and Peer Instruction.   ILD is a highly structured sequence of demonstrations with predictions and discussions with students that was developed at Tufts by Ron Thorton and the Center for Science and Math Teaching.  Peer Instruction is a method created by Eric Mazur, a Professor of Physics and Applied Physics at Harvard University.  It involves stopping several times during a class and asking a question that is usually multiple choice.  Students are then given time to discuss the question amongst themselves before voting on the answer.  This is followed by some discussion from students on why they voted for a particular answer and then either further discussion with Tobin or preferably a demonstration that illustrates the phenomena being addressed in the question.

Motivation and Goals
When Tobin first started teaching, he modeled his teaching on the way he had been taught:  “The professor stands up at the front of the room, writes a lot of stuff on the blackboard, explains things in as cogent, clear, concise and maybe amusing manner as possible, does some demonstrations, and we all sit there patiently and write down our notes.”

Initially, this method worked for Tobin.  Over time, however, he became dissatisfied with it as he began to notice that students weren’t getting out of it what he had hoped for.  He also became aware of a whole field of research in physics education where people were looking systematically at what students learned and what they didn’t learn.  The research was pretty convincing that the method of teaching that he had been using really didn’t work.

The research also showed that what were believed to be indicators of student learning in physics education really weren’t.  In physics education, students are often given complicated problems to solve.  The belief was that if the students could solve the problems they understood the physics behind it.  One study disproved this by first teaching students to solve complicated physics problems and then asking them some simple physics questions.  Though the students could solve the problems, they couldn’t answer the questions.   The results showed that the students had been taught how to do complicated problems and not much about how the world works.

This research convinced Tobin that he had to find another way of teaching.  He began what he describes as a certain amount of stumbling around as he did a lot of reading and watched what other faculty were doing until he found some techniques that worked for him.  The research made him realize that “whatever you do you have to get the students involved.  This is hardly a secret in education anymore. Students learn and remember things that they do and not things that they hear.  The trick is to figure out a way to do that on scale.  It is pretty easy to do that if you are sitting with 3 or 5 students.  You can have a very interactive conversation.  How to do that in a class of 100 or 200 is much more of a challenge.”

Peer Instruction has become the main technique that Tobin employs in his large classes.  He uses it every day spending about 15 minutes of his 50 minute class period on questions.  He has his students vote with hand held devices called clickers.  The clickers are not essential to the pedagogy but make it easier to implement.  In the past, he had students vote with colored pieces of paper that they held up.

Tobin explains that the greatest challenge in using this approach is coming up with good questions.  For him, it is a trial and error process of testing a question on a class and seeing how students respond to it.   The trick, he stresses, is to find questions that will give students an opportunity to start reasoning and be able to have a useful discussion.  If a question is too easy, the students will know the answer instantly and the discussion is over.  If the question is too difficult, the students will not be able to grasp it and have a good conversation about it.  Tobin also looks to homework, exams and the literature to identify issues that students have problems with.   He then tries to find questions that will bring those problems to the fore.

Tobin points out that it is important to not let students vote on an answer until they have had a chance to discuss the question first.   He has also found that demonstrations don’t work unless you get students to commit to an answer ahead of time.  If students are committed to a particular answer, they are more engaged in the outcome of the demonstration.   Before doing a demonstration, Tobin will ask for volunteers to explain why they chose a particular answer.  If the answer is incorrect, Tobin will explain why after he completes the demonstration.

Data that Tobin has collected from teaching 3 semesters of introductory physics classes shows that students absolutely love the peer instruction method and the clickers.  On a survey he gives each semester to his classes, over 90% of the students said he should keep doing peer instruction and using the clickers.  Students also rated the in-class questions as the piece of the class that they found the most useful to their learning.

Tips for Teaching

  1. As Eric Mazur points out in his book on peer instruction, instructors should use the expensive textbook that students are required to purchase as a resource to supplement what is presented in class.  This frees up the professor to focus on things that he feels are important using more interactive techniques like Peer Instruction and ILD.  Tobin tells his students, “I am not going to reproduce everything that is in the text book.  You need to go and read it.  I’m going to pick out the things based on my experience and expertise that I think are the challenging, interesting or important pieces that deserve time in the classroom, the parts that will give you trouble or where I have something to add that is not in the textbook.”
  2. In teaching, wrong answers based on some kind of reasoning are fine.  As a teacher you can’t even be implicitly critical of students for having the wrong answer.  You can’t express disappointment or disapproval in any way and you certainly can’t grade the students on the basis of right or wrong answers.  You want them to be invested in the process as they are already invested in getting the right answer.
  3. Technology is always something that you have to keep your eye on.  You need to evaluate   technological innovations to see how useful they are.  A lot of technology is not great but there are some tools that really lend themselves to simulation and demonstration.  However, you need to make sure that whatever you do is in the service of teaching something.  You should never use technology for the sake of technology.

Lessons Learned (reflection)
When reflecting on his teaching career at Tufts, Tobin remarks, “All of us here at Tufts whether we are on the faculty or are students are here because we had great teachers. If you start asking kids or adults about the people who had real influences on where they wound up and their accomplishments in life, you will almost always find a teacher on the list.”

He explains that teaching is one of the most rewarding and important things you can do and stresses that it really is a craft. You need to know not only your subject but also how to teach it.  Tobin sees Tufts as remarkable place in that regard: “You can get really get a terrific physics education here. We have outstanding physics faculty and research opportunities and an outstanding group of other students that you can learn from. At the same time, we have an education school that is one of the strongest around particularly in the areas of math and science pedagogy. They are up and involved in the latest and deepest research on what really works and why and how students think. This is an extraordinary opportunity to learn from the best both about the subject and about how that can really work in real classrooms.”

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