We recognize our friends' faces. And we're not alone. Many social animals can identify individuals of their own species by features of their faces. That's important, because they need to be able to change their behavior depending on who they meet. And a recent research has shown that some species of monkeys, birds, and domesticated (家养的) animals can even tell different faces apart by looking at photographs alone.
Ethologist Léa Lansade of the French National Research Institute for Agriculture, Food and Environment did an experiment to find out how well horses can recognize individual people in photographs.
She and her team first taught the horses how to “choose” between two side-by-side pictures by touching their noses to a computer screen. The horses were then shown photos of their present keeper alongside faces of unfamiliar humans. They had never seen photos of any of the people before. The horses correctly identified their current keeper and ignored (忽视) the stranger's face about 75%of the time. In fact, even though the horses didn't get it right every single time, they were at least as correct in picking out their earlier keeper as they were at identifying their present one.
The results suggest that not only can horses differentiate between familiar and unfamiliar human faces, they also naturally understand that photographs are two dimensional representations (二维呈现) of real life, without any other intimations such as smell or sound. And they're even better at this than our oldest animal parter, the domestic dog.
In addition, horses seem to have a strong long-term memory for human faces, like their long lifespan and history of domestication. In future experiments, the researchers would like to test whether looking at photos of people that they have had bad experiences with in the past might cause horses to act anxious or even avoidance. So maybe think twice before doing anything that might give a horse a long face.
