Dolphins may be thought of as “a kind of alien intelligence sharing our planet” and “the closest we’ll come to encountering ET.” Although all species on Earth descend from a common ancestor, humans and dolphins have been on different evolutionary paths for aeons, resulting in the massive differences we see today.

As with any animal, it’s important not to fall into the anthropocentric trap of evaluating dolphin intelligence on a scale that places us at the top. In fact, as the following 10 facts go to show, dolphin intelligence (and often cetacean intelligence in general) is actually worlds apart from our own, and in a category that doesn’t bear comparison—except, perhaps, insofar as to say that they are to the sea as we are to the land… minus the drive to oblivion.

10. They’re basically Facebook with fins

“A dolphin alone is not really a dolphin,” says Lori Marino, an expert on dolphin intelligence. “Being a dolphin means being embedded in a complex social network. Even more so than with humans.” Researchers have identified three levels of alliance within dolphin society. The most intimate are between pairs or trios of males who work together over decades to guard the females they successfully court. These combine into larger, second-order teams or alliances of up to 14 members that steal females from other groups, and these can remain intact for 16 years or more. Then there are the third-order alliances, “armies” in a sense, that come together for larger disputes.

Despite the remarkable stability of these alliances over time, dolphins also appear to be fickle. The same two dolphins may be friends one day and foes the next, and—unlike primates—these relationships may depend on the situation, e.g. which other dolphins are nearby. Naturally, keeping track of these complex social networks requires a hell of a lot of brain power.

9. They interact intelligently with humans

Dolphins have worked with humans for millennia—from giving rides to the ancient Greeks to helping Brazilians catch fish to planting bombs for the Soviet Union. They also play games with us, sometimes with just as much enthusiasm as with each other, and enjoy showing off—whether it’s by decorating their fins with our snorkels or forming circles with ribbons to jump through. Importantly, they often engage in this behavior for its own sake—or for ours—without any reinforcement of food.

Dolphins have also been said to form protective circles around swimmers in peril, protecting them from sharks or buoying them to the surface to breathe. On occasion, they have even towed humans to shore.

But they’re not always so altruistic. One researcher was left to fend for herself when dolphins fled at the sight of a shark. And encounters with lone dolphins in the wild are not always friendly—at least not by human standards. Some have made aggressive sexual advances, such as attempting to mount swimmers while sporting erections, dragging people out to sea, or pinning them to the seafloor—sometimes causing serious injury.

Still, one of the only cases of death by dolphin appears to have been deserved; according to witnesses, the victim was trying to force a cigarette into the dolphin’s blowhole.

8. Dolphins “get high” recreationally

Dolphins’ innovative nature, as well as their outward signs of culture, are all signs of their high intelligence—but so is their “use of drugs.” You may have seen the video of adolescent dolphins passing a pufferfish amongst themselves, apparently getting high on the neurotoxin, before floating with their noses at the surface “as if fascinated by their own reflections.”

Well if humans are anything to go by, drug use appears to be strongly correlated with high IQ, probably because it suggests openness to new experience. Evolutionary psychologist Satoshi Kanazawa argues that people with higher IQs are more likely to use drugs because smarter people are attracted to “evolutionary novelties,” or in other words to trying new things. The ethnobotanist Terence McKenna went one step further to suggest that our evolution into Homo sapiens was actually catalyzed by the use of magic mushrooms.

Of course, it’s debatable whether these dolphins actively sought out and chewed on the pufferfish to elicit those specific effects (which, incidentally, could have killed them all off). Some researchers just see it as inquisitiveness. But, either way, it remains a sign of intelligence—a trait that favors novelty far more than the preservation of life.

7. They’re highly creative

Like many animals, dolphins can be taught to perform tricks. They can be trained to stand upright on their tails and skate backwards through the water, to wave their fins, to corkscrew through the air, and so on—all at the command of a human. But they can also decide on routines of their own. Given the command to “innovate,” for example, dolphins taught to do so will surprise their trainer with a maneuver entirely of their own choosing. And, interestingly enough, they can often be heard exchanging chirps and whistles in pairs before executing these maneuvers, suggesting they’re “discussing a plan.”

Dolphins also show signs of culture—the creation and handing down of traditions. Female bottlenose dolphins in Shark Bay, Western Australia, for instance, came up with a special way of detaching conical marine sponges from the seafloor and wearing them as protection while they forage with their noses in the sand. And mothers teach this skill to their sons and daughters—though it’s usually the females who engage in the solitary activity of ‘sponging’; males are more interested in forming alliances.

Such feeding strategies are specifically designed to suit the environments they’re in, which, given dolphins’ worldwide distribution, tend to be highly variable. Hence in Florida Bay, they can be seen circling schools of fish with a wall of mud and forcing them to leap out of the water, while off the coast of Patagonia, they herd anchovies into spheres before taking it in turns to gulp them down.

6. They’re always thinking

Unlike humans and other land-based mammals, dolphins appear to breathe voluntarily. Respiration isn’t an unconscious mechanism, but something they have to consciously do. (This is how one of the dolphins who played Flipper in the 1960s TV show was able to kill himself by refusing to breathe.) So how do they avoid drowning while they sleep? By remaining conscious.

Dolphins sleep with only half of their brains at once while the other remains fully awake, a type of rest known as unihemispheric slow wave sleep. Not only does this allow them to keep surfacing for air when they need to, but it also lets them keep an eye out for danger—literally: While the right hemisphere of the brain sleeps, the right eye stays open and alert, and vice versa as the dolphin alternates between the hemispheres to fully rest the brain. This process takes roughly four hours—two for each side—and rarely will they sleep without company.

It’s unknown whether dolphins dream during this time, but they appear to get little rapid eye movement (REM) sleep—the phase during which dreams are experienced. That said, a group of captive dolphins at a French dolphinarium were heard apparently sleep-talking in whale song, something they heard daily as part of the soundtrack to their public shows. Researchers suggested they were mentally rehearsing the following day’s performance; however, given this particular center’s controversial mistreatment of dolphins, perhaps they were really just having nightmares.

If dolphins do have dreams, they’re likely to be especially lucid given that they never fully shut out the world. Their dreams may resemble more of an augmented reality or fantastical overlay to their vision, as opposed to the more immersive virtual reality that we humans experience when we dream.

5. They have a language—just probably not as we know it

We’ve been studying “Dolphinese” for decades and still haven’t been able to translate it. Working with the assumption that “such a large-brained, highly social creature wouldn’t waste all that energy babbling beneath the waves unless the vocalizations contained some sort of content,” researchers are eagerly anticipating some kind of “Rosetta stone,” or in this case a pattern connecting sounds to behavior.

One device that researchers are using to find it is the CHAT (cetacean hearing and telemetry) box, which sends out and records dolphin sounds for researchers to associate with objects and events. Progress has been slow, but algorithmic analysis of recordings has revealed five fundamental units of sound from the whistles between mothers and calves. Eventually, researchers hope to record all such fundamental units of sound so they can recombine and broadcast them and then analyze whatever comes back.

While some are skeptical that a dolphin language actually exists, what’s clear is that they do at least use names. In fact, they’re the only species other than humans to refer to individuals in this way. It’s thought that each dolphin comes up with their own unique “signature whistle” as a calf—a sound by which others call or greet them—and remembers it for the rest of their life.

4. They may be telepathic

The scientist John C. Lilly founded the Communications Research Institute in 1959 with the hope of teaching dolphins to speak English. He assumed it must be possible not only because of their comparable brain size, but also because of the way they mimicked the tone and pitch of human speech, seemingly in a desire to learn.

Teaching them English was just the first step, though. Lilly was far more interested in what dolphins might one day teach us. In fact, he envisioned a future in which the “Cetacean Nation” might be recognized as a member state of the UN General Assembly, offering special insights into world affairs and government. This tantalizing prospect sparked the interest of NASA, who funded Lilly’s research as a framework for communicating with aliens.

Lilly was also granted a license to administer LSD to the dolphins he worked with—a drug held in high regard at the time (just as it is increasingly today). Interestingly, they became far more vocal than usual while under the effects of the psychedelic—especially when others (dolphin or human) were in the tank with them. One dolphin in particular that had been averse to humans ever since it was shot through the tail with a spear gun was suddenly less afraid, swimming over to Lilly and interacting with him for the first time since they’d met.

Lilly never managed to teach dolphins English, but he claims to have “spoken” to them telepathically. Whilst lying inside an isolation tank next to the dolphins’ pool, he said, the animals took him “in to the dolphin group mind” and communicated information “beyond words.” Others have reported similar experiences, such as the New Zealand trainer who, allegedly, had only to visualize what he wanted dolphins to do for them to go ahead and do it.

3. They “see” and possibly “paint pictures” with sound

Dolphins have an extraordinary talent for echolocation—similar to bats but in many ways superior, not least because sound travels faster in water. Within milliseconds, they can map their surroundings in three dimensions with minimal energy expenditure—unlike even our most advanced, energy-guzzling supercomputers, all of which fall short of such accuracy. In fact, dolphins can identify the size, shape, and speed of objects from hundreds of yards away. And they can even distinguish between outwardly similar objects (like a golf ball and a ping-pong ball) based on their internal density—kind of like x-ray vision. In the wild, this allows them to easily tell the difference between fish and other prey and the bubble “nets” that dolphins use to surround them.

Emitting clicks from the nasal sacs behind their foreheads, dolphins bounce vibrations off of objects to receive them back in the fat-filled cavities of the lower jaw. From there, they are conducted along auditory nerves to the middle ear and brain. Each click thereby creates a snapshot frozen in time, and a series can map a moving landscape. You can see a visual representation of a dolphin’s sonic worldview, based on actual echolocation recordings, here. While it might not look like much, keep in mind that such a (remarkably precise) mental image would be supplemented with input from their eyes as well, just as our senses work in concert. (Sound is more important to them than vision, though; hence military sonar exercises often result in the deaths of disoriented cetaceans.)

Some researchers now believe, as John Lilly did, that dolphins actually communicate in a kind of sono-pictorial form of language. In other words, they may create (not simply receive) “holographic acoustic images” to share with each other as a way of referring to objects, places, and perhaps even abstract ideas.

2. Their brains are huge (oh, and they used to be wolves)

One of the reasons we became so interested in dolphins in the first place was the enviable size of their brains: 1.6 kilograms to our 1.3. Of course, this doesn’t automatically make them smarter; elephants have much larger brains than we do, but they also have larger, and as a result fewer, neurons. Interestingly, though, dolphins have been found to possess more than twice as many neurons in the neocortex (the largest and most recently evolved part of the brain) as humans. Specifically, long-finned pilot whales (a type of dolphin) have an estimated 37.2 billion neurons in the neocortex, whereas humans scarcely have 16 billion.

While they have many of the same abilities, including empathy and theory of mind, they also have some that we don’t, such as echolocation. And their relatively superior brain power may also have something to do with the complexity of their social relations.

Go back far enough (3.8 billion years or so) and all life on Earth can be traced to a single species. But it’s interesting to note that as recently as 50 million years ago, dolphins’ evolutionary forebears actually roamed the land—not as semi-aquatic creatures but as wolf-like herbivores with long skulls, strong jaws, and little hooves instead of claws on their toes. It’s thought that as the species gradually re-adapted to the sea, its legs evolved into flippers or disappeared entirely, along with its hair, and its nostrils relocated to the top of its head as a blowhole. Meanwhile, their brains became larger and their inner ear bones adapted for echolocation as they became more communicative or sociable, all of which favored greater intelligence.

1. They qualify as “non-human persons”

That dolphins can recognize themselves in a mirror is a sure sign of self-awareness and one that most other animals fail at. They’re also fully aware of their body parts and know exactly who’s in charge of their movement—something even human babies are apparently unable to grasp. They even associate their pectoral fins with humans’ arms and their tails with human legs, waving or raising them to mirror whatever their trainers are doing.

Some ask whether dolphins should be treated as people in the legal sense. Others say they are most definitely people (or “persons”) in every sense. After all, they are sentient, they have emotions, they exhibit self-control, and they treat others in a more or less ethical manner—certainly no worse than humans do anyway. For what it’s worth, they also seem to understand death, appearing to mourn their dead by supporting carcasses at the water’s surface for upwards of half an hour—and sometimes for days, even as they start to decompose—before leaving them behind for good.

In fact, dolphins fulfill every criteria for personhood, including individual personalities. One study found dolphins’ personalities not only vary—in openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism—but also remain stable over time. In other words, dolphins are basically just people who live in the sea, which raises serious questions about keeping them in tanks.

To say that dolphins are as intelligent (or more intelligent) than humans may be going too far. But to say they’re the second most intelligent species after humans may not be going far enough. Because dolphins and other marine mammals—indeed all animals—are simply (or rather complicatedly) intelligent in different ways. And on that basis alone we should treat them as our evolutionary equals.