Facet-Based Instruction
Facet based instruction centers around the idea that students, faced with a problem situation, apply preformed ideas from previous experiences or construct ideas and reasoning to make sense of the situation. These ideas are what we call facets of student knowledge. For example, a student might come to an introductory physics class with the idea that heavy objects fall more quickly than light objects. This idea might be constructed out of more primitive ideas such as "there is a bigger push/pull down on the heavier object" and "the bigger a force, the more motion." Another student might come to the same class suggesting that all objects fall at the same rate, because she saw a demonstration at the science museum. Yet another student might suggest that "the heavier object will fall more slowly, because it is harder to get it going." These examples are some of the many facets students might bring to class or constuct when faced with a problem. Facets are both specific and diverse; different students are likely to have different facets pertaining to the same concept or situation. Jim Minstrell has compiled a list of physics facet codes.
The facets of thinking that students bring to the introductory physics class with them may be both productive and unproductive. A didactic teaching format runs the risk of providing students with only a superficial understanding of physics, without changing their underlying ideas. So if students learn that all objects fall at the same rate, they may still not understand why this is so, or under what conditions it is true. In fact, they may reason backwards to undo some of their productive ideas. For example, they may reason that if all objects fall alike, they must all be influenced alike by gravity (Minstrell and diSessa, 1992).
Facet based instruction seeks to utilize the ideas that students bring to class with them, and guide the students through a process of identifying and weeding out the unproductive ideas, and integrating the productive ideas into a complex understanding of the ideas of physics.
The first goal of facet based instruction is to identify students' preexisting ideas about an area of physics (gravity, for example) in a preinstruction quiz. The responses to the quiz will give the teacher an idea of the range of beliefs that students in the class hold about gravity, as well as any contradictions among these beliefs.
After determining students initial beliefs, the instructor designs a series of benchmark and elaboration lessons that are intended to challenge student beliefs. For example, a benchmark lesson to address the facet that heavy objects fall more quickly than light objects might be an experiment in which students drop two objects of similar size and different weight, such as a wooden ball and a lead ball, and observe the results. An elaboration lesson might involve students dropping a coffee filter and a wad of paper about the same size. The object of the benchmark lesson is not to prove students right or wrong, but to encourage students to support their beliefs with reasoning and to see where there are contradictions between their observations of what does happen and their explanations or interpretations as they attempt to make sense of the world. It is the role of the instructor to lead the students through their intellectual impasses, through follow-up discussions and experiences, hopefully expanding student knowledge to encompass beliefs more nearly like those of a physicist.
Finally, a crucial element of FBI is to have student assessment embedded within classroom instruction. We have developed a computer program called DIAGNOSER to aid student assessment. Student assessment gives the teacher and the student nearly immediate feedback as to where student understanding may still be confused.