When a study came out late in 2017 claiming that sheep could recognize faces as well as humans, it was unexpected, to say the least.

Although recent studies have shown that many domesticated animals have a keen knack for interpreting the behavior of humans, facial recognition relies on a specialized neural process that few non-primates have the cognitive architecture for. How could sheep have managed to buck the trend?

It turns out, maybe they haven't. Researchers from the University of New South Wales, Newcastle University and the University of York have published a rebuttal to the original sheep study, suggesting that some of its claims may have been exaggerated, reports Phys.org.

As facial recognition abilities are concerned, humans are the unquestioned masters. It seems easy for us to pick out a familiar face from a crowd, but it's a surprisingly complicated operation cognitively. In fact, it's taken decades of research to figure out how to get computers to recognize human faces, and they still don't measure up.

In the 2017 paper, the authors suggested not only that sheep could recognize faces, but that they could do so at a comparable level to humans. That's the crucial claim that the current rebuttal raises doubts about.

The first issue raised is the fact that the 2017 study didn't subject sheep to as rigorous of a test as a human might have faced. For instance, sheep were only asked to recognize four faces, all human celebrities. The sheep were shown different pictures of the celebrities over the course of three training sessions, then they were shown a picture of one of the celebrities and chose which of another set was the same person. Sheep got the correct answer 79 percent of the time.

Impressive, to be sure. But it's still significantly below human scores. Under such limited constraints as this test, most humans ought to be able to pick the correct answer at a rate nearing 100 percent of the time.

For humans to score at a rate similar to the sheep in this study, they would have to be tested using many more faces, and with only one training session. Sheep in the study were given three sessions. Furthermore, while the sheep were surprisingly successful at recognizing faces given to them in the experiment, they were less successful at recognizing the faces of their own real-life human handlers. This demonstrates that facial recognition didn't come naturally for these sheep; it was only under trained sessions that they pulled it off.

And so, it would seem that sheep are not quite so good at facial recognition as previously claimed — although, they still performed rather admirably. Exaggerated claims or not, the 2017 study at least demonstrated that non-human animals are more cognitively flexible than they have been given credit for.

Can sheep really recognize faces as well as humans? New research raises doubts
Experts disagree with a prior study's claims that sheep can recognize faces as well as humans. They say some of the clams may have been exaggerated.