Original image
Illustrator unknown via Wikimedia Commons // Public Domain

These Fish Can Recognize Human Faces

Original image
Illustrator unknown via Wikimedia Commons // Public Domain

We really need to stop underestimating our fellow creatures. A new study adds a talented tropical fish to the swelling ranks of non-human animals that can tell humans apart. The research was published in the journal Scientific Reports. 

Facial recognition is a vital but complex task—so complex that humans have an entire region in our brains dedicated to it. And because it’s such a sophisticated process, scientists used to assume that we were the only animals that could do it. Then that circle widened a little bit to include other primates. But that circle just keeps growing, and currently includes octopuses, bees, and at least four types of birds. This is, admittedly, kind of strange; with the possible exception of birds, none of these animals have any natural need to tell people apart. 

Nor do fish. And like the cognitive abilities of birds, bees, and cephalopods, fishes’ mental skills have been more or less written off until quite recently. With this fact in mind, a team of researchers from the UK and Australia decided to find out if fish were up to the task. 

One species, the archerfish (Toxotes chatareus), seemed especially well-suited for the experiment. Archerfish are amazing creatures with a super-cool hunting strategy: They wait near the water’s surface for an insect to land on a nearby leaf, then shoot a jet of water at the bug, knocking it into the water. 

Illustration: Pearson Scott Foresman via Wikimedia Commons // Public Domain

Their aim is superb, and their vision acute, which suggests fairly sophisticated mental function. It also makes them great experimental subjects, since they can be trained to choose an object or image by spitting at it. 

The new study consisted of training and two experiments. First, researchers set up a screen above a tank holding a single fish. To see if the fish could tell the difference between two faces, the scientists displayed two faces on the screen, then attempted to train the fish to spit water at only one of them whenever it appeared. The training worked, and quickly, too; within just a few sessions, all the fish had learned to spit at the right face.

Image Credit: Newport et al. 2016.Nature Communications

Then the researchers brought back the same fish and exposed them to lots and lots of faces—44, to be precise. The goal was to see if the fish could still pick out the face they learned in the first round of training. To make it even harder, the researchers then cut all the face images into oval shapes and displayed them in grayscale so the fish couldn’t rely on more obvious cues like face shape or color. 

But the fish didn’t need color or shape. As in their hunting, the archerfish were incredibly accurate when it came to spotting faces. In the first round of 44 faces, the fish subjects averaged 81 percent accuracy. Once the obvious cues were removed they did even better, selecting the right face 86 percent of the time.   

“Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces,” said lead author and Oxford University zoologist Cait Newport in a press statement. “The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces.”



Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:

Original image
Big Questions
Why Do Dogs Love to Dig?
Original image

Dog owners with green thumbs beware: It's likely just a matter of time before Fido turns your azalea bed into a graveyard of forgotten chew toys. When dogs aren't digging up your prized garden, they can be found digging elsewhere in your yard, at the beach, and even between your couch cushions at home. But what exactly is behind your dog's drive to turn every soft surface he or she sees into an excavation site?

According to Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, this behavior is completely normal. "When people say 'why do dogs dig,' the first thing that always comes to mind is 'well, because they're dogs,'" she tells Mental Floss. The instinct first appeared in dogs' wolf ancestors, then it was amplified in certain breeds through artificial selection. That's why dogs that were bred to hunt rodents, like beagles and terriers, are especially compelled to dig in places where such animals might make their homes.

But this tendency isn't limited to just a few specific breeds. No matter their original roles, dogs of all breeds have been known to kick up some dirt on occasion. Beyond predatory urges, Dr. Grigg says there are two main reasons a dog may want to dig. The first is to cool off on a hot day. When stuck on an open lawn with little to no shade, unearthing a fresh layer of dirt untouched by the sun is a quick way to beat the heat.

The second reason is to stash away goodies. Imagine your dog gets bored with chewing his favorite bone but knows he wants to come back for it later. Instead of leaving it out in the open where anyone can snatch it up, he decides to bury it in a secret place where only he'll be able to find it. Whether or not he'll actually go back for it is a different story. "There's a disconnect with modern dogs: They know the burying part but they don't always know to dig it up," Dr. Grigg says.

Because digging is part of a dog's DNA, punishing your pet for doing so isn't super effective. But that doesn't mean you should stand idly by as your yard gets turned inside-out. When faced with this behavior in your own dog, one option is to redirect it. This can mean allowing him to dig in a designated corner of the yard while keeping other parts off-limits, or setting up a raised flowerbed or sandbox especially to satisfy that urge. "You can get him interested in the area by burying a couple bones or some interesting things in there for him to dig," Dr. Grigg says. "I like the idea of buried treasure."

If your dog's motive for digging is more destructive than practical, he may have an energy problem. Dogs require a certain amount of stimulation each day, and when their humans don't provide it for them they find their own ways to occupy themselves. Sometimes it's by chewing up shoes, toppling trash cans, or digging ditches the perfect size for twisting ankles. Fortunately, this is nothing more walks and playtime can't improve.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at


More from mental floss studios