Rhesus monkeys found to see faces in inanimate objects too

A team of researchers at the U.S. National Institute of Mental Health has found that rhesus monkeys, like humans, recognize face-like traits in inanimate objects. In their study published in the journal Current Biology, the researchers describe experiments they carried out with monkeys looking at photographs and what they learned from them.

Humans are notorious for seeing face-like characteristics in inanimate objects—the likeness of an old woman in a sliced tomato, Jesus in a potato chip, etc. Such recognition is known as pareidolia, and has been studied extensively in humans. But does it also happen with animals? That is what the researchers with this new effort sought to learn. They chose a relatively obvious animal for a subject, rhesus monkeys. Not only are they more human-like than most other animals, but they are also very social, which prior work with humans has suggested is very strongly tied to pareidolia.

The team worked with five of the monkeys, showing them pairs of pictures on a computer screen while timing how long they looked at them. Prior research has shown that rhesus monkeys, like humans, tend to stare longer at faces than at other objects. The monkeys were shown pictures of objects that a group of humans had already approved as having face-like characteristics. They were also shown pictures of similar objects without face-like characteristics. And for comparison, they were also shown pictures of the faces of other rhesus monkeys.

The researchers found that the monkeys did, indeed, fixate on those images with face-like characteristics longer than similar objects without such characteristics—and strangely, longer even than they looked at the faces of other monkeys. They also fixated on features resembling eyes and mouths. The researchers discovered this by also using a camera with face-tracking software to note where the monkeys were focusing their attention.

The results of their experiments, the researchers note, suggest that rhesus monkeys do, indeed, recognize faces in objects, which makes sense, the team further notes, because face recognition for them is important for maintaining social contact in their natural environment.