When it comes to naming intelligent animals, most people would be forgiven for not including sheep on their short list. From their blank, expressionless stares to their tendency to flee and panic at the slightest sign of trouble, thousands of years of domestication have ingrained in most cultures a stereotype of sheep as dumb.

As farmers, herders and increasingly scientists will tell you, sheep are far from the mindless creatures we presume them to be. What's most surprising in fact, is that sheep share levels of intelligence previously only recorded in humans and non-human primates. A 2001 study for instance found that sheep are capable of not only recognizing 50 individual faces (sheep, as well as humans), but also remembering them for more than two years.

"The way the sheep's brain is organized suggests they must have some kind of emotional response to what they see in the world," study lead Keith Kendrick told the BBC.

Based on these earlier results, researchers at Cambridge University were curious if sheep could take these facial recognition skills and apply them to photographs. In the study, published Nov. 8 in Royal Society Open Science, the team explained how they trained eight female Welsh Mountain sheep to recognize the photographs of four celebrities: Emma Watson, Barack Obama, Jake Gyllenhaal and British journalist Fiona Bruce. Food pellets were offered as a reward for distinguishing the celebrities from photographs of other individuals.

You can see a demonstration of their training in the video below.

In a skills test that previously only humans have passed, the sheep were able to distinguish the photographic portraits of the celebrity faces from different perspectives. Like our own facial recognition abilities, there was a drop from 80 percent to 65 percent in performance with the tilted images.

"We know that sheep can recognize their handlers, but I was still impressed they could do this," Jenny Morton, a professor of neurobiology who led the study at the University of Cambridge, told the Guardian. "Face recognition is a sophisticated process, but they’ve got big brains, they see other sheep, and they use this processing to recognize one another."

Sheep join an exclusive club of species that can recognize human faces, including monkeys, dogs and horses.

The researchers say the next step may be to see if sheep can identify emotional expressions on human faces. Because their test setup is height adjustable, they may also extend the photograph test to other species such as dogs, pigs, goats and horses.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Oh, I know ewe! Sheep surprise scientists with facial recognition skills
Results from new study show the animals have advanced facial recognition comparable to humans, monkeys, and apes.