A cat makes a funny head when he feels the fart of another cat after having planted his nose in the anus of the latter. A grimace called "Flehmen reaction", a characteristic attitude common to several mammals, due to the organ of Jacobson allowing the cat to taste the smells with its vomero-nasal organ. He turns his chops up to allow the smells to go up by two small ducts located behind the incisors up to two bags filled with fluid in the nasal cavities charged to concentrate the odors. A true sixth sense.