Updated: Oct 2, 2019
Dogs with a flat face are referred to as brachycephalic dogs. Brachycephalic literally means “short head” and is characterized by a short snout and wider skull. Breeds that are brachycephalic include: Boston Terrier, French Bulldog, English Bulldog, American Bulldog, American Staffordshire Terrier, Boxer, Pug, Shih Tzu, Lhasa Apso, Pekingese, Bull Mastiff, Neapolitan Mastiff, English Mastiff, King Charles Spaniel, Griffon Bruxellois, Dogue de Bordeaux, Japanese Chin, Affenpinscher, and Shar Pei.
This short head characteristic is actually determined by a measurement called the cephalic or cranial index (CI). The width of the skull (long axis-point just above ear to ear) is multiplied by 100 and then divided by the length of the skull (short axis-mid brow bone to the most prominent point in the back of the skull). A ratio of 80 or more is considered brachycephalic.
long axis X 100 = CI
These breeds widely have very sweet personalities, are very social, and prefer to be around their humans. They come in all sizes but generally they are sturdy and compact with wide heads and short faces. These pups also tend to be very playful and have very expressive facial features.
An interesting study was done in 2016 which correlated different dog morphologies (or their form/structure) and behaviors. The scientists from the University of Sydney took over 67,000 dogs from 45 breeds and correlated their cephalic index, height, sex, and body weight with 10 subsets of behaviors known as the Dog Mentality Assessment (DMA). The behaviors were assessed by officials of the Swedish Kennel Club and included areas of play, socialization, chase, distance-play, sudden appearance of people, presence of a random “ghost-like” figure approaching, metallic noise and gunshot reactions.