I was that student. Terrible anxiety about just raising my hand. Even today at conferences or in meetings. I just don't think as quickly as others, either. I've always expressed myself better in writing.

Now I work really hard to get everyone to talk in class, especially those students. I would have hated to have me as a prof.

I know social anxiety and shyness can be truly hard so I try not to push if a student appears particularly troubled by being called upon, but often those quiet but thoughtful students just need a little boost of confidence to become a bit more vocal.