There are 6 general personality types of dogs that may help you figure out why your Duke seems so uninterested in others, they are:
• AGGRESSIVE
• CONFIDENT
• OUTGOING
• ADAPTABLE
• INSECURE
• INDEPENDENT
It sounds to me that Duke could either fall under the adaptable personality or the independent. Here's a little more information about those two specific personalities:
Adaptable:
The adaptable dog requires the least amount of supervision as he will adapt well and fit into most situations with ease. The adaptable is easy to handle, eager to please, cooperative and readily accepts either human or canine leadership due to their naturally submissive nature. The adaptable is a mixture of the outgoing and insecure, tending to be somewhat shy, reserved or fearful when initially thrust into a new situation, yet fitting in quickly and exhibiting some extroverted traits to a lesser extent than a true outgoing.
The adaptable will rarely if ever resort to violence in the resolution of disputes tending to lean more towards pure submission when confronted with an aggressive or confident type. However, as with any animal when pushed too far or placed in a position where they are fearful, they could snap or momentarily lash out in a defensive nature, tending to immediately follow this with further attempts at submission.
You will find this personality type easy to intimidate and in the presence of an overly strong human leader there is a tendency to misdiagnose them as having been previously abused due to the fact that they naturally lean towards the traits of the insecure as a method of finding their place in the pack. The general demeanor of the adaptable is gentle and affectionate and they make high quality family pets. They have a higher tolerance to being left alone than the outgoing or confident types and they will demonstrate less destructive or separation anxiety related behaviors.
The adaptable shows no real potential for conflict with any of the other personalities tending to have good compatibility with all. This is another reason that they make a great family pet as there is less concern about personality conflicts for families that already have another dog.
Independent:
The independent personality is basically the un-dog like dog and demonstrates traits that one could attribute to either a fox or a cat and not to a dog. This is not to say that the independent is non affectionate, it is just affectionate on its own terms and when it chooses to be. The independent tends to be very aloof and appear disinterested in human
interaction leaning more towards limited social interaction with other canines. Always appearing to be on the outside of the window looking in, rarely showing strong pack behavior or a high play drive the independent marches to the beat of its own drum.
The independent is the least likely to resort to violence in the resolution of conflict choosing to adopt more of a neutral role or flee the situation entirely. The independent when forced into a never before seen situation tends to freeze up and show a high level of anxiety, to include rapid heart beat, urination, defecation or a release of the anal glands. The independent can be very easy to intimidate when in the face of overly strong leadership or an overbearing owner. Like the insecure this personality does best on a diet of positive reinforcement; negative reinforcement or attempts to dominate it will only result in strengthening its independent and aloof nature.
Do not expect this dog to grow into a super loving, human attention seeking member of the family and understand that there is nothing wrong or askew with this personality that needs repair. The independent will exhibit little or no destructive or separation anxiety driven behaviors when left alone and will settle on a nice place to sleep. The independent
nature of this personality does leave it prone to wondering off or escaping as it does not have a strong bond to the family pack. It is unlikely that it will respond to yelling or frantic actions if it finds the opportunity to
leave a controlled environment and will continue to walk away as if it has not a care in the world while you call for it to return.
I hope this helps you to figure out your Duke.