Bringing Critical Thinking to the Classroom

I teach my first college courses in physics in a few weeks. College courses in science generally include a component which asks instructors to teach critical thinking. Reflecting on this piece as I prepare my classes, I thought it would be good to briefly revisit what it means to think critically and share that with readers.

Stephen Brookfield writes in his book “Teaching for Critical Thinking: Tools and Techniques To Help Students Question Their Assumptions” the four basic steps of critical thinking:

1. Identifying the assumptions that frame out thinking and determine our actions.
2. Checking out the degree to which these assumptions are accurate and valid.
3. Looking at our ideas and decisions (intellectual, organizational, and personal) from several different perspectives.
4. Taking informed actions.

The most important of these steps identifying assumptions, because we often don’t realize our thoughts on a subject are indeed assumptions and not facts based on observation.

As a teaching assistant, I would point out a simple example of these assumptions to students. I begin by asking what color their blood is while inside their blood vessels while I look down at the visible vessels in my hand. A surprising majority answer blue, due to both what they learned at an early age from their teachers, as well as the blue look to their blood vessels when viewed through the skin. It helps set the stage for the semester with an understanding that we all carry assumptions with us, and it is important to look for them and challenge them with experiment.

Edward Glaser defines critical thinking in a way more directly related to experience and experimentation. He writes:

“The ability to think critically, as conceived in this volume, involves three things: ( 1 ) an attitude of being disposed to consider in a thoughtful way the problems and subjects that come within the range of one’s experiences, (2) knowledge of the methods of logical inquiry and reasoning, and (3) some skill in applying those methods. Critical thinking calls for a persistent effort to examine any belief or supposed form of knowledge in the light of the evidence that supports it and the further conclusions to which it tends.

This is why it is important to keep students active in the classroom, and to make the class useful and meaningful to them. Once they are engaged, it brings an attitude change that engages them in Glaser’s first step.

University of Maryland professor Joe Redish demonstrates the difficulty in moving students past their assumptions. He points out one of the common questions on the Force Concept Inventory (FCI), which is a thoroughly researched test of concepts from the introductory kinematics-based college physics class. The question is one on gravity:

Two balls are the same size but one weighs twice as much as the other. The balls are dropped from the top of a two-story building at the same instant of time. The time it takes the ball to reach the ground will be: (1) About half as long for the heavier ball; about half as long for the lighter ball; (2) about the same time for both; (3) considerably less for the heavier but not necessarily half as long; (4) considerably less for the lighter but not necessarily half as long.

When many students who had finished the introductory physics class still didn’t get this question correct, Redish began to change the way he approached this basic concept. He would pose this question to the class. Then, he would go to the second floor while his students stood on the sidewalk below. When the balls reach the ground at the same time, the experience connects them to the concept, and students begin to realize their belief was an assumption, and one that was incorrect. It also introduces students to the idea of experimentation and observation.

While it is not possible to perform your own experiment and observation for every aspect of your life, by having an idea of how the process works, it gives a guide as to when another’s work can be trusted. If someone tells you your blood is blue in your veins, you can ask how they came to that conclusion. If someone tells you that two masses dropped from relatively small heights with enough mass and small enough surface area to ignore air resistance will reach the ground at the same time and describe how the experiment was performed, you can begin to trust that as more than just an assumption. As others repeat the experiment and demonstrate a similar effect, these other viewpoints can strengthen your own view.

Scientific educators are beginning to see the benefit of teaching through experimentation and critical reflection. Groups such as the Physics Education Group at the University of Washington, the Modeling Instruction Program at Arizona State University, and Eric Mazur at Harvard University all have approaches involving a more interactive classroom including Socratic questioning. Years of development, refinement, and measuring students pre- and post-course show this approach improves the integration of science knowledge. A Google search on Physics Education Research shows many universities seeing the value of integrating critical thinking in physics courses.

I encourage all of you to reflect on the concept of critical thinking. Are we all carrying assumptions that perhaps it is time we challenge? I look forward to bringing this way of thinking to my students. The evidence indicates the students benefit more from their courses by doing so. It also makes for a more scientifically aware and literate society.