Having had both large and small dogs, it does seem like the bigger they are, the more tolerant they are. However, I did find that what really set my littlest ones off was being swooped down on. A child (or anyone else, for that matter) approaching slowly and/or steadily from where the dog can see is less likely to get a reaction than someone reaching down suddenly from above ti grab or pet them. When introducing people to my Shih Tzu - the least tolerant of attackers-from-above - I found that raising her up higher helped a LOT. If she could greet someone at eye-level (which usually meant putting her up high on the back of the couch or a table) made a world of difference in how well she accepted new people. She LOVED people - ANY people. It was surprises that set her off!
