I tried to address this problem with minimal success. I'm sure I will have many more chances to try different solutions. I read a very interesting piece in the Chronicle of Higher Education (subscription required) about getting quiet students to talk. The author had a been a silent student due to her Appalachian upbringing and tried to find a way to get bright, quiet students to speak up in class.
Here is a excerpt from the article
"Is the problem," I asked, "that you don't know where your comments will fall on a scale of one to smart?" She nodded. "Let's fake it," I suggested, and, for the first time, she looked mildly hopeful. I e-mailed her a few questions before the next class discussion and told her to try out an answer on me before the class met. She duly, if tentatively, offered her electronic answer, and I responded with (justified) reassurance.(Source Talk to Me by Ashley Marshall) I look forward to trying something similar to this in my classroom in the future.The scheme worked. She turned bright pink when I asked the question, but she put up her hand, and I called on her. She was barely audible, but she delivered her answer, to which I was able to say honestly, "Right. Great response, and here's why it's important." I e-mailed her that evening to say how pleased I was, and how proud of her—and that we would do it again next week. We did.
The week after that, she stuck up her hand without prompting and delivered one of the smarter student comments of the whole term. She was thrilled. Again I wrote to reassure her, and in several of the remaining classes she had something to say. This technique has worked for a number of nonspeaking students since then, mostly female but occasionally male as well.
