As with all dog breed characteristics, head shapes have been greatly influenced by the selective breeding practices of their human masters. If a certain shape was thought to be beneficial for a certain function, man worked to create the ideal head type for that job.

Faces of dogs that were used as guard dogs, for example, were bred to resemble wolves, with their elongated muzzles and pointed ears. The massive undershot jaw of the Bulldog was created to function as a fierce weapon for use in bull-baiting and dog fights. Dogs that were used in racing events or to chase down prey were bred to have long, thin, streamlined heads.

Sometimes head types were genetically engineered purely on the subjective opinion of what was attractive to the human eye. Many companion dogs were bred to have large soulful eyes and flattened, human-like faces. Considered canine "human babies," Pugs were once shown at dog shows wearing necklaces and were awarded extra points for having comical, hairy moles.

Dog fanciers today have created the following terms to describe the basic head types found in dog breeds:

• Apple Head: Very rounded, with a dome-like skull. (Chihuahua)
• Blocky Head: Square, cube-shaped head. (Boston Terrier)
• Domed Head: Convex, even rounded top skull. (Cocker Spaniel)
• Broken-up Face: Receding nose, with a deep stop and undershot jaw. (Pekingese)
• Down Face: Muzzle has a convex incline from the top of the skull to the tip of the nose. (Bull Terrier)
• Dish Face: A head with a profile that forms a slightly concave shape. (Pointer)
• Snippy Face: Pointed, thin muzzle without much depth or width. (Saluki)