Wikis as Pedagogical Tools

This quarter I'm a TA for a class related to American history. I'm not a historian, but it's much better than last quarter. The class is being supervised by an excellent, highly experienced professor. It consists of a series of units on various aspects of American life. Each unit involves a lecture, a movie, and a set of readings. The lecture is conducted by a different professor from the department every week. This leaves a lot of work for the TAs, but in general the lectures are excellent. Excellent professor writes lucid assignments, which makes grading them much easier.

The other TA and I are both trying to use a wiki as part of the class. This week I introduced the wiki to the students in discussion. I set up the wiki with separate pages for each of the units.

The first assignment is for them to research major events in a particular decade of American history. I assigned this because after reading the first set of essays I realized that some of them were confused about basic chronology. One essay claimed that Americans were really happy when movies and movie theaters became available because then they didn't have to watch TV at home. I'm hoping that they will be able to research some basics that an educated person would consider common knowledge. I'm not as picky as Sasha Abramsky, I don't expect them to have heard the Beatles.

The goal is to get them thinking critically about American culture. I told them that participation in the wiki is part of their discussion participation grade. They are free to add information to the wiki as they like, but I want to come up with assignments as well because this is a gen. ed. class and I think giving them some structure will help them figure out how to participate. There is also a chat function they can use to enter questions and comments about the class. Any ideas about how to get students participating in an online discussion?