Some canine traits are very clearly "nature" and are a result of genetic influence. Many of the most obvious traits are physical, such as coat length and color. Breeders have used knowledge of genetic inheritance to create litters of puppies to meet breed-specific standards and looks. Other genetic traits may be less visually obvious and relate more to their temperament, but still play a role in building the individuality of a dog. For example, a dog's energy level or trainability can be, in part, determined by the genetic influence of his parents.
A study researched the fearful nature of several pointer dogs. Initially, the dogs were separated into two groups: highly fearful or tolerant. From there, breeding was done in each group, mating fearful with fearful and tolerant with tolerant. Within 1-2 generations, puppies from each group exhibited predictable behaviors. The puppies with fearful parents were much less exploratory, and more easily startled than their peers. They were timid and uneasy around humans. The other group of puppies, bred from more tolerant parents, were more outgoing and played freely with others. To expand this study, researchers placed fearful puppies with tolerant parents for cross-fostering, but there was little to no change in their nature. The behavioral traits in both groups of puppies are attributed to the genetic inheritance of their parents. Their anxious personalities are a biological aspect of their temperament.
Nurture, or the experiences that a dog has, however, cannot be discounted when considering a dog's behaviors. Puppies are very moldable and trainable animals. There are many strategies an experienced trainer can use to influence a dog's behaviors. For example, sitting and waiting for an "ok" command before eating is not in a dog's nature. Their instinct is to dive in and start eating. Training a dog to wait, and control his behavior, is an effect of nurture and environment. There are many simple examples of nurture affecting a dog's behaviors, but there are also extreme cases that highlight the power that interactions and conditioning can have on a dog. For example, dogs used in fighting rings are often considered quite dangerous. Their aggression comes, in part, from breeding highly volatile dogs and creating a very powerful bloodline. However, some very skilled, experienced, and patient people have been able to overcome their aggressive temperaments. The nurture and care provided, over time, can condition dogs to be more comfortable around people and other animals.
A final example to show the combination of nature and nurture is service dogs. Facilities like Bergin University breed their own puppies from the highly accomplished service dog lines they've trained. Choosing the most capable service dog parents creates a strong possibility that the puppies will have good trainability and temperaments. However, many of the puppies are exited from the training program at a young age because they do not meet the very high expectations for service dogs. Though the dogs came from the parents (nature) and were trained with similar techniques (nurture) some dogs perform better than others. Variations in either the specific genetic inheritance or the specific trainer can contribute in small ways that result in varying abilities in dogs. Nature and nurture are both very strong influencers on canine behavior.