I have a Cairn terrier that is also shy or timid. She cowers and tucks her tail when ever someone raises their voice or she hears a loud noise. I think it is just genetic with her because this is the 3rd Cairn I bought from the same breeder and all the others are very outgoing. She is also a quiet girl that has never let out a peep in her crate--even the very first night we brought her home when she was 8 weeks old. I think of them like people and everyone has a different personality. Some people are talkative, demanding, loud, quiet or soft spoken. That is her in people terms--shy, quiet, gentle, low keyed, and very soft spoken BUT absolutely NORMAL for her and I love her for it. She is a very peaceful dog!