The prenatal period

When a pregnant animal is petted her litter is more docile, and this effect can be heightened by caresses to the new-born. The 'caress effect' facilitates relaxation, digestion and emotional attachment and thus socialisation as well.

Dehasse describes a number of experiments where the results suggest that when a pregnant dog is given a friendly and caring human environment with affectionate physical contact, the friendliness and emotional balance of the puppies is increased.

A good reason for choosing a small home breeder. I've no doubt that Rosie got lots of pats and tummy rubs throughout her pregnancy.