How much is that doggie in the window? Not much, but if that window belongs to a pet shop, you might want to reconsider taking Rover home according to a new study from the University of Pennsylvania School of Veterinary Medicine.

Dubbed C-BARQ, Penn's study had veterinarians and animal researchers take an online survey to screen animals for behavioral issues, subsequently allowing other users to compare their dogs to others in the database. The finding, perhaps not surprisingly to the dog trainers among us, was that puppies coming from pet stores have a much higher risk of developing those behavior problems due primarily to increased aggression, fearfulness, sensitivity and separation-related issues.

It has long been common knowledge to dog trainers and vets that pet store puppies, which often come from the dreaded "puppy mills," can be somewhat off, but Penn's study represents the first of its kind. Now, there is concrete scientific evidence that purebred dog owners would do better going right to the breeder.

Primarily, that's because pet store puppies are not socialized within the first few months of their lives when coming from puppy mills. The result, of course, is an anti-social animal that is fearful of its surroundings instead of trustful. But while fear is a large factor in an animal's behavior, study leader Dr. Frank McMillan says that it is not the only factor, citing elements like prenatal stress.

Commercial kennels (aka puppy mills) generally involve the use of small enclosures and have very little positive human interaction, which study leaders say could engrain the fear response so heavily in pet store animals. The solution, should you find yourself with a pet shop pup, is to begin training early.

Otherwise, it might be smart to brush up on Pennsylvania's puppy lemon laws.

[Decoded Science]