I've been in Human Resources for over 25 years, it is actually very noticeable, to me. It's reflected in tone and response to questions. Hiring managers will also sometimes look for candidates who fit into the group in regards to temperment. If it is a generally positive, cohesive group, the hiring manager is not going to hire someone with a bad attitude, even if they try to hide it.
Shy is one thing, a bad attitude is something entirely different.