At first, you're grateful. At the beginning of the semester, with a classroom full of skeptical students not yet ready to speak up, you usually have at least one student who always seems ready to raise his hand or blurt out answers. This student seems like a godsend: He (it's almost always a he) actually listens to what you're saying and is confident enough to want to test out his ideas in the public space of the classroom.
But soon you start to suspect that this overeager student may be hurting more than helping. He dominates discussions, always jumping in before anyone else gets a chance, sucking all the air out of the room. It doesn't matter if his answers are correct, or whether you encourage him or not. It becomes a self-sustaining pattern: The other students quickly realize that they don't need to respond; if they hold back long enough, they know that the dominant student will speak up.
In my last column, I wrote about the difficulties involved in getting quiet or uncooperative students to contribute to class discussions. Motivating them to speak up can take a lot of work. But it can be just as challenging to have one or two students who talk too much. A few garrulous students can end up crippling class debate and cutting off the possibility of a wide-ranging discussion involving the whole class. How should you respond?