Sudden Change

• If a dog is normally social and happy to be around people but then suddenly acts aloof, a veterinarian visit is in order. Sometimes pain or medical conditions may cause behavioral changes in dogs.
  
  

Breeds

• Some dog breeds are known to act more aloof. Working dog breeds which have been bred primarily to watch over property and livestock may be naturally reserved toward strangers.
  
  

Expert Insight

• Sometimes, a reserved, almost shy temperament may be due to genetics. It is unusual for a shy puppy to be born from gregarious, confident parents, explains veterinarian Ron Hines.
  
  

Socialization

• You should properly socialize shy puppies or puppies belonging to dog breeds known to be aloof. The ideal time frame for proper socialization generally ranges from when the puppy is 3 weeks old up until 14 weeks of age.
  
  

Prevention/Solution

• If the dog was not proper socialized and it consequently developed an aloof temperament, you can try to expose it to all kinds of people gradually and cautiously. Allowing strangers to toss treats toward the dog may help it make positive associations encouraging more friendly and social behaviors.