A New Method for Assessing Critical Thinking in the Classroom

摘要

To promote higher-order thinking in college students, we undertook an effort to learn how to assess critical-thinking skills in an introductory biology course. Using Bloom's taxonomy of educational objectives to define critical thinking, we developed a process by which (a) questions are prepared with both content and critical-thinking skills in mind, and (b) grading rubrics are prepared in advance that specify how to evaluate both the content and critical-thinking aspects of an answer. Using this methodology has clarified the course goals (for us and the students), improved student metacognition, and exposed student misconceptions about course content. We describe the rationale for our process, give detailed examples of the assessment method, and elaborate on the advantages of assessing students in this manner.nnSeveral years ago, we launched a journey toward understanding what it means to teach critical thinking. At that time, we were both biology instructors working together on teaching an introductory biology course at Duke University, and we wanted to help students develop higher-order thinking skills—to do something more sophisticated than recite back to us facts they had memorized from lectures or the textbook (i.e., what many of them had been asked to do in previous biology courses).nnThe justification for our journey is well supported by the science education literature. Many college and university faculty believe that critical thinking should be a primary objective of a college education (Yuretich 2004), and numerous national commissions have called for critical-thinking development (e.g., AAAS 1989, NAS–NRC 2003). Yet when trying to implement critical thinking as an explicit goal in introductory biology, we found ourselves without a well-defined scheme for its assessment.nnAnd we were not alone. Despite the interest among faculty in critical thinking as a learning goal, many faculty believe that critical thinking cannot be assessed or they have no method for doing so (Beyer 1984, Cromwell 1992, Aviles 1999). Consider a 1995 study from the Commission on Teacher Credentialing in California and the Center for Critical Thinking at Sonoma State University (Paul et al. 1997). These groups initiated a study of college and university faculty throughout California to assess current teaching practices and knowledge of critical thinking. They found that although 89 percent of the faculty surveyed claimed that critical thinking is a primary objective in their courses, only 19 percent could explain what critical thinking is, and only 9 percent of these faculty were teaching critical thinking in any apparent way (Paul et al. 1997). This observation is supported by evidence from other sources more specific to the sciences, which suggest that many introductory science, technology, engineering, and math (STEM) courses do not encourage the development of critical-thinking abilities (Fox and Hackerman 2003, Handelsman et al. 2004).nnWhy is it that so many faculty want their students to think critically but are hard-pressed to provide evidence that they understand critical thinking or that their students have learned how to do it?nnWe identified two major impediments to the assimilation of pedagogical techniques that enhance critical-thinking abilities. First, there is the problem of defining “critical thinking.” Different definitions of the term abound (Facione 1990, Aretz et al. 1997, Fisher and Scriven 1997). Not surprisingly, many college instructors and researchers report that this variability greatly impedes progress on all fronts (Beyer 1984, Resnick 1987). However, there is also widespread agreement that most of the definitions share some basic features, and that they all probably address some component of critical thinking (Potts 1994). Thus, we decided that generating a consensus definition is less important than simply choosing a definition that meets our needs and consistently applying it. We chose Bloom's taxonomy of educational objectives (Bloom 1956), which is a well-accepted explanation for different types of learning and is widely applied in the development of learning objectives for teaching and assessment (e.g., Aviles 1999).nnBloom's taxonomy delineates six categories of learning: basic knowledge, secondary comprehension, application, analysis, synthesis, and evaluation (box 1). The first two categories, basic knowledge and secondary comprehension, do not require critical-thinking skills, but the last four—application, analysis, synthesis, and evaluation—all require the higher-order thinking that characterizes critical thought. The definitions for these categories provide a smooth transition from educational theory to practice by suggesting specific assessment designs that researchers and instructors can use to evaluate student skills in any given category. Other researchers and even entire departments have investigated how to apply Bloom's taxonomy to refine questions and drive teaching strategies (e.g., Aviles 1999, Anderson and Krathwohl 2001). Nonetheless, the assessments developed as part of these efforts cannot be used to measure critical thinking independent of content.nnThe second major impediment to developing critical thinking in the classroom is the difficulty that faculty face in measuring critical-thinking ability per se. It is relatively straightforward to assess students' knowledge of content; however, many faculty lack the time and resources to design assessments that accurately measure critical-thinking ability (Facione 1990, Paul et al. 1997, Aviles 1999). A large body of literature already exists showing that critical thinking can be assessed (e.g., Cromwell 1992, Fisher and Scriven 1997). The critical-thinking assessments that have been most rigorously tested are subject-independent assessments. These assessments presumably have the advantage of allowing measurements of critical-thinking ability regardless of the context, thus making it possible to compare different groups of people (Aretz et al. 1997, Facione et al. 2000). Previous studies have demonstrated a positive correlation between the outcomes of these subject-independent tests and students' performance in a course or on a task (e.g., Onwuegbuzie 2001). Such studies serve to illustrate that critical thinking per se is worth assessing, or at least that it has some relationship to students' understanding of the material and to their performance on exams. Still, generalized assessments of critical-thinking ability are almost never used in a typical classroom setting (Haas and Keeley 1998). There are several problems with such general tests, including the following: Faculty doubt that the measurements indicate anything useful about discipline-specific knowledge.n n Administering these tests takes time away from the content of the course and can be costly; thus, they are viewed as “wasted” time.n n Most faculty lack the time to learn the underlying structure and theory behind the tests, and so it is unclear to them why such a test would be worthwhile.n nnnRecognizing the problems with standardized, discipline-independent assessments of critical thinking, we developed an assessment methodology to enable the design of questions that clearly measure both the content we want students to know and the cognitive skills we want them to obtain. Ideally, this methodology should allow for discipline-specific (i.e., content-based) questions in which the critical-thinking component can be explicitly dissected and scored. Furthermore, we built on the work of others who have used Bloom's taxonomy to drive assessment decisions by using this taxonomy to explicitly define the skills that are required for each question. Finally, we crafted a system for developing scoring rubrics that allows for independent assessment of both the content and the skills required for each question. It is this methodology we have begun applying to introductory biology.