Shyness is also a relative measure, because people get social fears in different situations. I've met shy people who were very outspoken as soon as they had the keyboard in front of them, confident and bossy people who crumpled in social situations with people they didn't know well; outgoing people who froze as soon as they saw a video camera on them.
It's about not knowing what will happen. Many shy kids can't read certain emotions clearly. The researcher suggest that the cure could well begin with sitting these kids down to go through through facial expressions, both in real life and on a screen, giving feedback on identifying them to build confidence in their ability to assess people's moods correctly. Next is role-playing possible scenarios, so you find out what the fears are.
Writers have many fears which often inhibit their writing; working through those takes courage, as well.