The common raven (Corvus corax) is a large, intelligent bird found across the Northern Hemisphere. Ravens have long captivated human imagination with their dark plumage, eerie vocalizations, and apparent cleverness. But just how intelligent are these birds compared to other animals? Scientific research over the past few decades has gradually revealed the complex cognitive abilities of ravens.
Ravens are part of the corvid family, which also includes crows, jays, and magpies. Corvids have the largest brains relative to body size of any bird group. This extra neural power enables complex cognitive skills like tool use, bartering behavior, creation of mental maps, and probable self-recognition. Ravens, along with some crow species, are considered the most intelligent corvids.
Physical Abilities
Ravens have several physical adaptations that allow advanced intelligence. Their large brains have more neurons packed into the forebrain region than many mammals of similar size. Ravens also have more nerve connections between the two brain hemispheres compared to other birds. This enables coordination between analytical left-brain functions and creative right-brain skills.
Ravens have strong visual recognition abilities rivaling primates. They have forward-facing eyes like humans, allowing binocular vision with overlapping fields of view. This helps ravens judge distances accurately when swooping down toward food sources or diving in flight. Ravens can also see ultraviolet light, allowing them to spot urine trails and other signals imperceptible to humans.
In one experiment, ravens demonstrated an exceptional ability to distinguish between faces of individual humans, even when lighting conditions changed. After being trained to recognize facial images of people wearing ski masks, the ravens could still identify those individuals in photos without the ski masks.
Communication and Vocal Learning
Common ravens have a wide repertoire of vocalizations. Their calls range from deep, croaking caws to harsh grating sounds. Ravens can mimic noises like animal calls and human speech. Some have been taught to say words when raised in captivity.
Ravens engage in vocal learning similar to parrots, bats, whales, and humans. By imitating sounds in their environment, ravens develop new vocalizations not innate to their species. Young ravens typically spend time listening to adult calls before perfecting their own vocal expressions.
Researchers found ravens can even mimic human speech simply by overhearing conversations, without being deliberately trained. This ability implies ravens recognize speech as meaningful communication between individuals. It also demonstrates an ability to encode and reproduce novel sounds after minimal exposure.
Tool Use and Manipulation
Ravens are one of the few animals that use tools in the wild without human training. For example, some ravens use rocks to crack open hard nuts and shellfish. Others will select a twig, remove side branches, and use this “hook tool” to probe crevices for grubs.
Ravens also craft rudimentary tools in captivity if given appropriate materials. In one experiment, ravens used plastic blocks and sticks to create a stepping stool high enough to reach an out-of-reach food reward. This showed imagination in envisioning a possible tool before creating it.
Common ravens are incredibly dexterous with their large beaks. They can pick up tiny objects, carry awkwardly shaped items, and rotate small pieces in the beak with precision grips. In some tests, ravens performed as well or better than chimpanzees and young human children on intricate object manipulation tasks.
Caching and Retrieval of Hidden Objects
Ravens cache extra food when it is abundant so they can retrieve it later during hard times. To succeed at this, ravens must have spatial memory capacities that allow them to accurately recall the locations of their hiding places.
Researchers have performed caching experiments that suggest ravens have extraordinarily retentive memories. In one trial, ravens were allowed to cache and retrieve various small food items in an aviary with 128 potential hiding spots. The ravens consistently located almost all their caches even when tested after 22 days. This outperformed other corvids like scrub jays that could only remember for up to 13 days.
Ravens also seem able to plan ahead for conditions in the future based on memories of their caching activities. When caching items, ravens will preferentially hide food in locations that will be blocked from view later on. This implies an ability to mentally visualize future circumstances.
Social Intelligence and Deception
Common ravens live in socially complex groups with ever-changing relationships. To navigate raven society, these birds employ tactics of teamwork, deceit, reconciliation, and score-keeping of favors granted and received.
Ravens engage in cooperative hunting with their mates. After discovering a large food bonanza like a dead moose, raven pairs will recruit other ravens to help defend the carcass from competitors. Studies of raven couples show they spend much more time together than pairs of similar-sized birds like hawks.
Ravens also practice deception to hide food finds from others. If a raven uncovers a cache while being watched by other birds, it may pretend to “cache” the item in several locations instead of the real one. Alternatively, ravens may retrieve a food item and then fly a long distance before actually caching it, to confuse onlookers.
When ravens’ own caches are stolen by other ravens, the victims show clear signs of social understanding. Instead of aggressively attacking the thief, victims adjust their behavior and later reconcile by preening or sitting next to the culprit – while also hiding food far away in private next time.
Possible Self-Recognition
Self-recognition is an advanced cognitive ability previously identified only in humans, great apes, dolphins, elephants, and magpies. To test for self-recognition, scientists apply a colored spot to an animal’s body in a location it can’t see without a mirror. If the creature spontaneously notices and investigates the spot while looking in a mirror, this indicates awareness of its own body and appearance.
In a 2017 study, researchers tested common ravens for self-recognition by placing small colored dots on the birds’ feathers. When provided with mirrors, the ravens turned and pivoted to examine themselves and touch the dots. This suggests ravens may indeed possess self-recognition, although more research is needed. If confirmed, it implies ravens have introspective minds that can think about themselves as individuals.
Play Behavior
Juvenile common ravens love to play. They chase each other through the air, hang upside-down while grabbing each other’s feet, and engage in communal games with objects like stones or twigs. Ravens also playact fighting, taking turns in dominant and subordinate roles.
Play is rare in the animal kingdom outside of mammals. Scientists think play indicates intelligence because it requires imagination and teaches young ravens physical skills, social bonding, and cognitive flexibility. The most intelligent animals tend to play the most. That ravens play at least as much as chimpanzees hints at advanced intelligence.
Problem-Solving Tests
Researchers have tested raven intelligence using complex puzzles that require logic, insight, and sequential problem solving. In these experiments, ravens manipulate objects like plastic or wooden shapes to release food rewards.
Ravens consistently perform as well or better than primates like chimpanzees and orangutans on such tests. In one trial, ravens excelled at a puzzle requiring them to trade a bottle cap for a food item, and then deposit the cap into a vending machine to release more rewards. Four out of five ravens mastered this in less than two hours.
In another test, ravens worked together to pull a series of ropes simultaneously to raise a food basket within reach. The ravens spontaneously understood they needed to coordinate and pull together, without requiring step-by-step training. Very few animal species demonstrate this kind of cooperation and sequential reasoning.
Brain Imaging Studies
Scientists have scanned raven brains to identify regions linked to intelligence and social interaction. One study revealed that raven brains light up in cell zones associated with insight and judgment when confronted with a problem-solving challenge. Regions tied to sociality and motivation were more active when the birds could watch others solve the problem first.
Researchers also found ravens have an unusually large and well-developed nidopallium caudolaterale region of the forebrain. This area is linked to executive functions like working memory, behavioral inhibition, and reward-seeking. A large nidopallium caudolaterale likely supports the raven’s capacities for causal reasoning, flexibility, imagination, and innovation.
Conclusion
Common ravens have proven their smarts across an array of physical and mental tests. A large brain with sophisticated neural architecture allows ravens to perceive, manipulate, play, communicate, cooperate, deceive, and probably recognize themselves. Ravens have demonstrated cognitive skills on par with great apes that were previously considered unique to humans.
While not yet fully understood, raven intelligence could emerge from a combination of factors. Their hyper-social lifestyle may select for cooperation, deception, and score-keeping of relationships. Caching foods and pilfering others’ caches may drive highly retentive spatial memory. Manipulating and nibbling all kinds of objects with their versatile beak may enhance object cognition. And living in harsh northern climates with unpredictable food sources could favor innovation, problem solving, play, and mental flexibility.
So how smart are ravens? Smarter than most birds and many mammals. They possess extraordinary intelligence that in some ways matches the great apes and even surpasses them. Common ravens merit their reputation as clever members of the corvid family. Their advanced cognitive abilities impress both scientists and casual observers, leaving little doubt these birds have highly developed, multifaceted intelligence.