Scientists and enthusiastic dog owners alike have long quibbled about what attributes or tendencies make one animal smarter or more intelligent than another. But as animal researchers have applied various intelligence tests to a wider net of living things in recent years, the dividing lines have only gotten murkier.
Earlier this year, a group of 40 researchers from top universities around the globe signed on to the New York Declaration on Animal Consciousness, arguing that recent studies suggest far more animals may have the capacity for consciousness than previously thought and that there is “strong scientific support” for attributing consciousness to mammals and birds. The researchers say there’s even a “realistic possibility” of consciousness in other, less remarkable vertebrates, like reptiles, amphibians, and fish, and possibly even cephalopods and other animals without a backbone.
Here are a few of the ways animals are forcing scientists to rethink consciousness and cognition, ranging from the more familiar to others far less so.
Elephants
Elephants are widely considered some of the most intelligent mammals outside of primates thanks to their exceptionally large brains and strong social bonds. The giant, long-trunked mammals have been observed mourning their dead, and in some cases, even burying them. They have notoriously long-lasting memories which makes them adept problem solvers and tool users. Outside of nature, humans have leaned on those skills and traits to exploit elephants as circus performers. Other research has shown elephants capable of replicating one another’s calls with high levels of precision. An elephant in the Bronx Zoo in 2006 also proved it was capable of recognizing itself in a mirror, a key sign researchers associate with self-awareness.
Dogs
Dog owners are often nearly as enthusiastic about praising their animal’s intelligence as a new parent. And, on a species level, science suggests they have good reasons for the excitement. Though precise levels of measurable intelligence vary by dog breed and individuals, researchers estimate some canine’s are capable of learning a sort of meaning of over a hundred words. Dogs are notoriously skilled at implicitly understaffing humans’ emotions and can reportedly exhibit signs of jealousy. At least some of that intelligence, researchers believe, is likely a byproduct of evolving alongside humans for thousands of years.
Pigs
Pigs are amongst the most intelligent animals that are still commonly eaten by humans worldwide. Researchers have observed pigs using mirrors to examine their surroundings and ultimately forage for food. More recently, a family of Visayan warty pigs were reportedly observed using sticks as tools to build nests, a behavior not previously observed. Some of the most striking recent research involving pigs was published in the journal Frontiers in Psychology in 2021, where researchers from the Pennsylvania State University taught a pig to use a joystick to play a rudimentary video game.
Dolphins
Though there’s no agreed upon way to “rank” animal intelligence in its many forms, dolphins, by any measurement, would stack up towards the top near humans. A 2016 study published in the journal Physics and Mathematics, claims dolphins communicate amongst each other with a highly complex sting of sounds that closely resembles words and sentences. Unlike other animals, the dolphins observed rarely interrupted each other. Dolphins have learned to cooperatively hunt alongside fishermen in Brazil and have reportedly assisted human swimmers during shark attacks. Part of the reason for the sea mammal’s remarkable intelligence is likely due to its exceptional brain size to body weight ratio, which is the second largest for all animals only behind humans. In terms of sheer size, a bottlenose dolphin brain bests humans.
Parrots
Though parrots are mostly known for loudly repeating human language, (sometimes to embarrassing ends) the depth of their intelligence stretches much further. Recent studies showed parrots were able to succeed at logic games that typically stump five-year-old humans. Some of the birds have even figured out how to communicate using modern video conferencing technology. Researchers from Northeastern University, MIT, and the University of Glasgow recently trained 18 parrots to use a specially designed tablet to communicate with one another. When the parrots rang a bell their caretaker would show them the tablet screen which had pictures of other parrots they had previously video chatted with. The parrots repeatedly requested to chat with their long-distance friends.
Crows
Crows have continually exhibited a grasp for numbers and signs of other signs of intelligence researchers once believed were only attainable by humans. Research from the University of Tübingen have demonstrated crows are capable of counting out loud up to four, a skill likely attributed to their particularly large forebrain which is typically linked with statistical reasoning. Though many associate tool use with mammals, some crows are capable of crafting sticks into hooked tools which they then use to pick insects out of trees.
Octopus
Octopus, maybe more than any other animals, have garnered attention in recent years thanks to a groundswell of research, articles, and books highlighting their seemingly familiar but totally foreign forms of intelligence. In captivity, octopi can reportedly tell different humans apart and have even been observed spraying ink at individuals they dislike. Some have even been observed shooting ink at lightbulbs to make their environment darker. The eight-armed mollusks are notoriously curious and border on mischievous. A two-spotted octopus living in the Santa Monica Pier Aquarium in 2009 was blamed for turning a valve that ended up leaking 200 gallons of seawater into the facility.
In the wild, octopuses are among nature’s best shape shifters. Octopuses, and other cephalopods, are capable of altering their skin tone and color on the fly to blend into their surroundings and avoid predators.
Bumblebees
Bumbless, along with ants, have often confounded critics who attempt to keep insects out of conversations related to animal intelligence. Researchers from Queen Mary University of London in 2016 taught bumblebees to pull a string in order to receive a reward. More impressively, other bees learned to perform the same task simply by watching their comrades. Bee also has an impressively nuanced grasp of counting and can even reportedly understand the concept of zero, or, none, something typically only observed in humans, parrots, and apes.
Crayfish
Crayfish, close cousins of the more widely known lobster, may exhibit signs of anxiety treatable through Valium-like drugs. Though the ancient looking sea creatures have existed for hundreds of millions of years, scientists haven’t typically considered them to possess enough intelligence to be considered sentient.
Researchers from the University of Bordeaux called that assumption into question in a 2014 study where they exposed a test group to an electrical field, which was intended to induce a potentially anxious experience. Following the zap, the crayfish were placed into separate tanks which had darker and lighter areas. Crayfish typically prefer darker areas but shocked subjects would avoid the lighter areas outright. When the researchers examined those crayfish further, they saw they were producing high levels of serotonin which occurs in other species when they are trying to counteract anxiety. More telling still, the researchers injected those crayfish with an anti-anxiety medication and found they eventually overcame their inability to explore the lighter areas of the tank.
Cleaner wrasse
The common cleaner wrasse fish, which averages just around four inches in length and is found abundantly in coral reefs, wouldn’t seem like an obvious contender for an animal intelligence list at first glance. And yet, researchers have shown they seem to be able to complete the mirror-mark test, one of the most widely used experiments to determine if an animal can recognize itself. Even dogs typically fail this test.
A group of researchers writing in PLOS Biology placed 10 of the fish in a tank with a mirror. Though most of the fish immediately thought the reflection was another animal, several of them began spending more time with their reflection. They even began swimming upside down and performing other behaviors considered unusual for the species. When researchers marked the fish with a brown dot, some of them appeared to recognize it in the mirror and even tried to scrub it off.
