However if your young child has a preference for a small rodent, such as a guinea pig that runs free in the house, you should reconsider your choice of breed if you opted for a terrier. Some terriers were developed especially to hunt rodents. So, whatever your choice, keep to it, but ask about its compatibility to competent people before getting an unwelcome surprise. Although there is nothing impossible with good training, the fact of having experience in the domain will certainly facilitate your task with certain types. There are some obvious differences between the various breeds, even different types in a same breed, on the level of affinities in the training.
Some breeds learn more quickly than others, some have a character more or less dominate, etc.
The effort and time that you will have to dedicate to the training of your puppy will be in function of your choice of breed and individual. Are there essential things that your dog must or must not have. Now is the time to ask yourself these questions. This will permit you to avoid many problems, either in selecting the right breed, or in learning to educate your animal appropriately. The fact of already having a dog might influence your choice.