Using Argument Diagrams to Improve Critical Thinking Skills in 80-100 What Philosophy Is Maralee Harrell1 Carnegie Mellon University Abstract After determining one set of skills that we hoped our students were learning in the introductory philosophy class at Carnegie Mellon University, we designed an experiment, performed twice over the course of two semesters, to test whether they were actually learning these skills. In addition, there were four different lectures of this course in the Spring of 2004, and five in the Fall of 2004; and the students of Lecturer 1 (in both semesters) were taught the material using argument diagrams as a tool to aid understanding and critical evaluation, while the other students were taught using more traditional methods. We were interested in whether this tool would help the students develop the skills we hoped they would master in this course. In each lecture, the students were given a pre-test at the beginning of the semester, and a structurally identical post-test at the end. We determined that the students did develop the skills in which we were interested over the course of the semester. We also determined that the students who were able to construct argument diagrams gained significantly more than the other students. We conclude that learning how to construct argument diagrams significantly improves a student’s ability to analyze, comprehend, and evaluate arguments. 1. Introduction In the introductory philosophy class at Carnegie Mellon University (80-100 What Philosophy Is), as at any school, one of the major learning goals is for the students the students to develop general critical thinking skills. There is, of course, a long history of interest in teaching students to “think critically” but it’s not always clear in what this ability consists. In addition, even though there are a few generally accepted measures (e.g. the California Critical Thinking Skills Test, and the Watson Glaser Critical Thinking Appraisal, but see also Paul, et al., 1990 and Halpern, 1989), there is surprisingly little research on the sophistication of students’ critical thinking skills, or on the most effective methods for improving students’ critical thinking skills. The research that has been done shows that the population of US college students in general has very poor skills (Perkins, et al., 1983; Kuhn, 1991; Means & Voss, 1996), and that very few college courses that advertise that they improve students’ skills actually do (Annis & Annis 1979; Pascarella, 1989; Stenning et al., 1995). Most philosophers can agree that one aspect of critical thinking is the ability to analyze, understand, and evaluate an argument. Our first hypothesis is that our students actually are improving their abilities on these tasks. We thus predict that students in the introductory philosophy course will exhibit significant improvement in critical thinking skills over the course of the semester. In addition to determining whether they are improving, though, we are 1 I would like to thank Ryan Muldoon, Jim Soto, Mikel Negugogor, and Steve Kieffer for their work on coding the pre- and posttests; I would also like to thank Michele DiPietro, Marsha Lovett, Richard Scheines, and Teddy Seidenfeld for their help and advice with the data analysis; and I am deeply indebted to David Danks and Richard Scheines for detailed comments on many drafts.Argument Diagrams Improve Critical Thinking Skills 2particularly interested in the efficacy of various alternative teaching methods to increase critical thinking performance. One candidate alternative teaching methods in which we are interested is instruction in the use of argument diagrams as an aid to argument comprehension. We believe that the ability to construct argument diagrams significantly aids in understanding, analyzing, and evaluating arguments, both one’s own and those of others. If we think of an argument the way that philosophers and logicians do—as a series of statements in which one is the conclusion, and the others are premises supporting this conclusion—then an argument diagram is a visual representation of these statements and the inferential connections between them. For example, in the Third Meditation, Descartes argues that the idea of God is innate. It only remains to me to examine into the manner in which I have acquired this idea from God; for I have not received it through the senses, [since] it is never presented to me unexpectedly, as is usual with the ideas of sensible things when these things present themselves, or seem to present themselves, to the external organs of my senses; nor is it likewise a fiction of my mind, for it is not in my power to take from or add anything to it; and consequently the only alternative is that it is innate in me, just as the idea of myself is innate in me. (Descartes, 1641) The argument presented here can be diagrammed as shown in Figure 1. FIGURE 1 An argument diagram representing an argument in Descartes’ Third Meditation. Note not only that the text contains many more sentences than just the propositions that are part of the argument, but also that, proceeding necessarily linearly, the prose obscures the inferential structure of the argument. Thus anyone who wishes to understand and evaluate the argument may reasonably be confused. If, on the other hand, we are able to extract just the statements Descartes uses to support his conclusion, and visually represent the connections between theseArgument Diagrams Improve Critical Thinking Skills 3statements, it is immediately clear how the argument is supposed to work and where we may critique or applaud it. Recent research on argument visualization (particularly computer-supported argument visualization) has shown that the use of software programs specifically designed to help students construct argument diagrams can significantly improve students’ critical thinking abilities over the course of a semester-long college-level course (Kirschner, et al. 2003; van Gelder, 2001, 2003). But, of course, one need not have computer software to construct an argument diagram; one needs only a pencil and paper. To our knowledge there has been no research to determine whether the crucial factor is the mere ability to construct argument diagrams, or the aid of a computer platform and tutor, or possibly both. Our second hypothesis is that it is the ability to construct argument diagrams that is the crucial