PBL and Lectures
The Trouble with Lectures
Think of each student's brain as a complex map of reality. Every map is unique. Tested and familiar, those resilient maps pay off in terms of survival and well being. They represent individual experience. A brain's genetic structure, especially emotional temperament, determines the way experience is understood and mapped. Of course brains are far more complex than we can grasp at this time, but this simplified version is helpful. It confounds our own misleading mapping of brains as stuff that absorbs, records, or contains.
To learn students must re-make their maps and that means making and breaking connections in the brain. If students are highly motivated to learn by curiosity, interest, or a need to adapt, they will struggle long and hard to re-think and re-design their maps. Indeed, that struggle with its attendant joys and sorrows is what we think of when we recount the impact of learning on one's views of self and world. But if students are not motivated they may conclude that cognitive changes aren't worth the effort. They resort to memorizing, utilizing their short-term memory to regurgitate information on tests and in projects. That results in a quick loss of information and little or no change in their maps of reality.
Students resist the struggle to learn when they see no need for re-organizing. Consider this is not a flaw of character, or a generational failure, but a lack of interest based on their best judgment. As instructors we cannot directly motivate the need to learn, we have to demonstrate a learning payoff in the form of skills and knowledge that have an immediate use. Grades don't create a need to learn. They create a need to get a grade. That undermines the motivation to learn.
What students know (or believe) determines what they can learn. Student conceptions and misconceptions filter information. Telling students about a subject -- describing, explaining, giving examples, etc. works well when student maps are congruent with the subject or when students are emotionally committed to learning. In other words, lectures are effective when conveying new information to experts or eager novices. Lectures are least effective when conveying information to uninterested novices. See Donald A. Bligh, What's the Use of Lectures, 1972.
The human attention span is about 15 to 20 minutes long. Many years of research confirms this finding. (See http://www.upenn.edu/almanac/v50/n15/teaching.html) When reading or listening to tapes, students can stop and go back over material when they lose focus or do not understand. When listening to an on-going lecture they cannot. Studies show lectures are as effective, but no more so, than assigned readings or tapes in conveying information. They are not effective in promoting thought. If you think hard during a lecture you miss what comes next. And surprisingly they are not effective in changing attitudes.
So long as we limit lectures to 15 minutes or less to convey information they are a part of a useful educational repertoire. Unfortunately, studies indicate lectures dominate 85% of classroom time. And this often is true in problem-based learning classes. We over-use lectures, as if we were handy with screwdrivers and tried to build houses using that familiar tool all of the time.
How Can We Use Lectures Effectively in Problem Based Classes?
The most important step is to prepare novices before lectures by arousing curiosity and activating what they already know and believe on the topic. Technically speaking, we can provide students with advanced organizers. Some examples:
A lecture on learning:
- Have students write short stories about their experience on a three by five card and discuss them with peers.
- Individual story: What was the best class you ever had?
- Collaboration: Share your results and each group come up with a consensual model of the best class ever.
A lecture on Kant's categorical imperative:
- Individual story: When was the last time you successfully lied to your parents and what were the results?
- Collaboration: Share your story with the person next to you.
A lecture on the structure and characteristics of causal theories:
- Individual: Construct a theory about what you will have to do to get an A in this course?
- Collaboration: Share your theories and each group construct the most effective theory you can.
For other examples see: http://webphysics.iupui.edu/jitt/Examples/BioWarmup.html
Here is the process -- a thinking activity followed by a lecture.
1. Thinking Together
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2. Short Lecture
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If you introduce a class with a lecture you model active instructor/passive student. If you introduce a class with an activity like a problem, or a story, you will find more students interested and engaged. As students get used to the rhythm of activity-lecture-activity they may contribute to your lectures with questions and comments.
Just in Time Lectures
In problem-based learning courses there are times when instructors need to explain and explicate. They can provide just-in-time lectures (5- 10 minutes long) when students encounter difficulties in formulating or solving problems. This presents some difficulties.
Students are used to lectures, they seem "normal" to them, and when they are having difficulties formulating problems, finding resources, or proposing solutions they may hope for an instructor's lecture to do their work for them. Much of their previous experience in school has been of the "find out what the instructor wants me to say, think, or do," variety. Many believe that lectures will relieve them of organizing and understanding the material of a course.
When students struggle, instructors are tempted to rescue them with a lecture. Instructors are used to lectures, usually that is how they were taught and seldom have they encountered alternatives. Lecturing enables almost complete control of the classroom situation. Instructors strive to be clear, concise, and give good examples; precisely doing the thinking they want students to do. They repeat examples and principles, aping the practice that students need to do for themselves. Thus even just in time lectures can short-circuit the learning process. We can move toward directed discussions to avoid this.
Examples
Expert Solutions: When listening to students present problem formulations or solution alternatives, instructors hear and see many errors. It is important that they point these out and discuss them. One way to do that is to provide an "expert perspective or solution" - a handout or a mini lecture in the form of here is what an expert would say, advise, do in this situation and here is the reasoning behind that. Have students compare their solutions to the expert example and write a short evaluation of their performance. Or ask students for a short written statement about the difference between the expert's and a student's or a team's approach.
Student Examples: When students are confused about a principle or process they ask for examples. What they need are concrete examples from their experience - and there is the rub. These kinds of examples are not easy. The age/experience gap means that instructors share little of the students' world. Two possible solutions are:
- Try examples out on a student/consultant who can suggest changes to improve their concrete relevance.
- Present the problem to students themselves by asking them to create examples of the principle or idea. You can offer one example - or refer back to the example in the assigned readings and then say, "OK, get together with your team and generate two or three better examples of principle x. You have fifteen minutes. Put your examples in a word document that we can display."