Teaching critical thinking in a developmental biology course at an American liberal arts college.

We all expect our students to learn facts and concepts, but more importantly, we want them to learn how to evaluate new information from an educated and skeptical perspective; that is, we want them to become critical thinkers. For many of us who are scientists and teachers, critical thought is either intuitive or we learned it so long ago that it is not at all obvious how to pass on the skills to our students. Explicitly discussing the logic that underlies the experimental basis of developmental biology is an easy and very successful way to teach critical thinking skills. Here, I describe some simple changes to a lecture course that turn the practice of critical thinking into the centerpiece of the learning process. My starting point is the "Evidence and Antibodies" sidelight in Gilbert's Developmental Biology (2000), which I use as an introduction to the ideas of correlation, necessity and sufficiency, and to the kinds of experiments required to gather each type of evidence: observation ("show it"), loss of function ("block it") and gain of function ("move it"). Thereafter, every experiment can be understood quickly by the class and discussed intelligently with a common vocabulary. Both verbal and written reinforcement of these ideas dramatically improve the students' ability to evaluate new information. In particular, they are able to evaluate claims about cause and effect; they become experts at distinguishing between correlation and causation. Because the intellectual techniques are so powerful and the logic so satisfying, the students come to view the critical assessment of knowledge as a fun puzzle and the rigorous thinking behind formulating a question as an exciting challenge.