The question of the next smartest animal to humans is less a search for a single titleholder and more an investigation into the various forms intelligence takes across the animal kingdom. Cognitive ability is not a single, linear scale, but a complex spectrum of specialized skills adapted to ecological challenges. Determining a “smartest” animal requires evaluating achievements in separate domains, such as social complexity, tool use, and abstract thought. Candidates for the title are diverse, encompassing mammals with large, folded brains, small-brained birds, and even invertebrates with decentralized nervous systems.
Defining and Measuring Non-Human Intelligence
Scientists use behavioral and anatomical metrics to assess intelligence, moving beyond the simple measure of absolute brain size. A more refined structural measure is the Encephalization Quotient (EQ), which compares an animal’s actual brain size to the expected size for its body mass. Humans possess the highest EQ, around 6.5, but this ratio alone does not capture the full picture of cognitive ability across different animal classes.
Behavioral tests provide a clearer picture of functional intelligence, focusing on observable skills. These include tool creation and use, requiring an understanding of cause and effect, and self-recognition, often tested using the mirror self-recognition test. Problem-solving capacity, such as navigating complex mazes or solving multi-step puzzles, is a common metric. The complexity of social behavior, including the ability to form alliances, deceive rivals, and transmit learned skills across generations, known as culture, represents a high level of cognition.
The Primate Contenders: Our Closest Analogues
The great apes—chimpanzees, bonobos, and orangutans—are often considered the most obvious candidates due to their close genetic relationship with humans. Their cognitive achievements center around sophisticated social dynamics and an advanced capacity for symbolic thought. Chimpanzees engage in intricate social politics, forming complex, shifting coalitions to achieve and maintain alpha male status. This requires continuous networking, “bluffing,” and monitoring relationships within the group.
Bonobos, in contrast, have a matriarchal social structure where female-female bonds are the most important, and conflicts are frequently resolved through socio-sexual behavior rather than aggression. These different social strategies demonstrate a flexibility in social cognition that mirrors human political variation. Furthermore, some apes have shown a remarkable capacity for planning, such as when they select and transport tools for a task and store them for use up to 14 hours later.
Studies into symbolic communication further illustrate their cognitive depth, though they are often subject to debate. The bonobo Kanzi spontaneously learned to communicate using a keyboard of geometric symbols called lexigrams, acquiring a vocabulary of nearly 400 signs. Kanzi also demonstrated an understanding of spoken English, responding correctly to novel sentences requiring an understanding of word order, such as “Take the vacuum cleaner outdoors”. Similarly, the gorilla Koko learned a version of American Sign Language, using over 1,000 signs to express complex emotions, invent new compound words, and even lie, although her grammatical comprehension remains debated.
Cognitive Giants of the Ocean
The ocean’s cetaceans, primarily dolphins and whales, represent a separate evolutionary path to high intelligence, possessing vastly different brain structures than primates. Bottlenose dolphins have an Encephalization Quotient above 5, exceeded only by humans among non-cetaceans. Their brains feature highly developed neocortices with intricate folding patterns, and the long-finned pilot whale has more neocortical neurons than any other mammal examined to date, including humans.
Their intelligence manifests primarily in their complex social lives and communication systems adapted for an aquatic environment. Dolphins use signature whistles that function similarly to individual names, allowing them to address each other directly. They exhibit evidence of culture by passing down learned behaviors, such as using marine sponges as tools to protect their beaks while foraging on the seafloor. Whales and dolphins form alliances and engage in cooperative hunting techniques taught and maintained across generations, highlighting their advanced social learning and cultural transmission.
Avian and Cephalopod Mastery
Intelligence is not restricted to large-brained mammals, as evidenced by the cognitive mastery of certain birds and invertebrates. Corvids, a family that includes crows and ravens, possess a high density of neurons in their forebrains, allowing for complex thought despite their small brain size. New Caledonian crows are famous for their tool-making, modifying natural materials like twigs and leaves to extract insects.
These birds also demonstrate advanced causal reasoning, such as in the Aesop’s Fable task, where they drop stones into water-filled tubes to raise the liquid level and access a treat. Their ability to plan multiple steps ahead and solve novel problems rivals that of some primates.
In a separate lineage, octopuses and other cephalopods have evolved remarkable intelligence without a centralized vertebrate brain structure. Octopuses are renowned for their escape artistry and camouflage abilities, relying on rapid, context-dependent problem-solving. They demonstrate high-level cognition by solving multi-step puzzles, navigating mazes, and even using tools, such as carrying coconut shell halves for future shelter.
Ultimately, the “next smartest” animal depends on the metric chosen: great apes excel in symbolic communication and social politics, cetaceans in complex culture, and corvids and octopuses in novel, non-social problem-solving. This illustrates that intelligence is a mosaic of different cognitive strengths.