A cow’s ability to tell the difference between her friends Ruby, Belle, and Jewel — what scientists call individual discrimination — forms the basis of social relationships and hierarchies, as well as responses to familiar versus unfamiliar individuals.
Like cows, a range of animals can tell the difference between individual members of their species, including dogs, elephants, and pigs. Importantly, individual discrimination underlies an animal’s ability to recognize family members and familiar individuals, as well as make fine distinctions among the individuals who comprise her social circles.
Cows demonstrate ample ability to differentiate between individuals of their own species. In just a few trials, heifers can learn to discriminate familiar cows, and they can retain that information for at least 12 days.
Heifers can also differentiate between individual cows who, at the outset of a test, are not all equally familiar to them. Not only can cows tell the difference between other cows, they also demonstrate a concept of species. That is, they can organize “cows” into a conceptual group distinct from other kinds of animals, and they can accomplish this mental organization even with the visual differences in individual cows’ appearances. In just a few testing sessions, cows discriminated between photographs of various kinds of cow faces from the faces of members of other species.
In another study, heifers differentiated between two-dimensional images of familiar and unfamiliar cow faces. This finding is particularly striking: It suggests that the cows could mentally sort the images of cow faces into the categories “familiar” and “stranger.” This study also suggests that the cows treated the images as visual representations of real individuals, much as we would likely interpret a family photograph in a neighbor’s home as a visual representation of an actual family.