Mistakes in teaching--presentations

The semester is nearly wrapped up; its lessons are becoming clearer. One came clear to me last night--if your goal is to get students to determine the most important things they've learned, a presentation is a weak way to do it.

Last night students in my freshman seminar class gave final presentations. The purpose of the presentation was to get students to identify the key things they learned about science and ethics (the topic of the seminar) by asking them to distill their learning in a presentation.

The guidelines were simple--pick a scientific issue with significant ethical implications. Create a powerpoint that analyzes those implications using a set of questions from one of our readings. Submit the powerpoint as an artifact in their e-portfolio. In the presentation, focus on one part of the powerpoint--the student's view of how society should respond to the ethical issues. Five minutes to present.

The presentations were, in general, weak. Some students took the brief presentation time as a sign that they didn't need to prepare well. Others tried to fit their entire powerpoint into 5 minutes. Students who are confident in class discussion were tongue-tied by having more time to prepare and the attention of the entire class.

Many of these things are predictable--the result of students making decisions about how to allocate limited time, feeling under pressure in their other classes, etc. But there was one thing that I might not have predicted. The students indeed learned a lot about the issue and the ethics in their preparation. But that learning didn't come out in the presentation. Instead, it showed up in their responses to questions from the group.

For example, one presentation on the dangers associated with playing with the movement of subatomic particles made almost no sense and was alarmist (the student suggested that cooling an atom to absolute zero could cause a black hole to emerge on earth). But in response to questions from classmates, he clearly explained how super-cold temperatures affect subatomic movement and the implications of that for the stability of matter. In other words, presentation showy and not convincing; responses to questions thoughtful and measured.

The same thing happened with several other presentations/questions. So I am left wondering why. Why would a prepared presentation with clear guidelines elicit less thoughtful work than an unscripted question and answer session? What does this mean for the wisdom of assigning student presentations at all?