It sounds like the start of a bad party joke: What do you get when you mix two octopuses, a Star Wars action figure and ecstasy? But a recent experiment did just that, and it revealed that at a neuromolecular level, we have more in common with these tentacled cephalopods than you might think.

Neuroscientist Gül Dölen of Johns Hopkins University and fellow researcher Eric Edsinger, an octopus researcher at Marine Biological Laboratory in Woods Hole, Massachusetts, arranged an experiment with two octopuses and either a stormtrooper or Chewbacca action figure. With the toy in a chamber on one side of a tank, and a cephalopod friend in another chamber, a sober octopus would spend more time with the inanimate object. But add a little MDMA to the equation, and the doped-up octopus starts to get cozy with its pal, as reported today in the journal Current Biology .

“I find it fascinating that the experimenters were able to chemically elicit prosocial behavior in octopuses, which are commonly quite nervous about approaching conspecifics,” says David Scheel, a marine biologist who specializes in octopus behavior at Alaska Pacific University and was not affiliated with the new study.

MDMA, called ecstasy or Molly when taken recreationally, essentially causes a flood of serotonin in the brain. The drug is known for the happy-go-lucky, heart-eyed effect it has on people. By studying ecstasy’s effects on octopuses, the team realized something that they didn’t expect—the same genetic and neurological infrastructure that’s linked to prosocial behavior in humans is also present in other organisms. Specifically, a gene called SLC6A4 codes a serotonin transporter in both humans and octopuses that’s known to be the binding site of MDMA.

“The impact MDMA has on the social behavior in this study is compelling and may help fill in many of the missing pieces for understanding the role of serotonin in social behaviors,” says L. Keith Henry, a molecular neuroscientist at the University of North Dakota who was not involved in the study.

Because vertebrates diverged from invertebrates more than 500 million years ago, it may come as a bit of a surprise that humans and octopuses share common neurological functions at all—our last shared ancestor probably resembled some kind of worm-like sea creature. It’s easy to assume that people don’t have much in common with our eight-legged, under-the-sea friends.

For starters, our two arms and two legs pale in comparison to the eight suction-cup-covered appendages that give the octopus its name. These versatile sea creatures have three hearts, but no bones , and they’re known for squirting ink at their predators (an ability we regrettably lack). The octopus is a master of disguise , using camouflage to blend in naturally with its surroundings—something we need special gear to achieve. And most relevant to this study, octopuses are asocial and solitary beings, avoiding others of their own kind unless it’s time to mate.

But for all our differences, we know octopuses share a fundamental trait with humans: intelligence . The animals are clever enough to use tools and can open child-proof pill bottles when put to the test. Because of their smarts, researchers have long suspected that octopuses might serve as suitable animal models to study the inner-workings of neuromolecular anatomy, Dölen says.

“Octopuses’ brains are different from ours,” she says. “They don’t have the brain regions we study in humans, yet they can do remarkable things.”

Vertebrate brains and invertebrate brains often look and operate quite differently because the two groups split so long ago, evolving separately for millions of years. To really get a sense of what’s happening in the brain to cause social behaviors, scientists need to take a look at the genetic operations under the hood.

The researchers cross referenced the genomes of 21 species, including humans. The gene SLC6A4 perfectly matched in humans and octopuses, which is why the team believes MDMA has the same effect on the two species.

The genetic connection between the species is particularly relevant because MDMA has recently been praised as “breakthrough therapy” in clinical trials, used alongside additional therapeutic treatments to combat conditions like PTSD. Serotonin signaling also has a clear association with many aspects of Autism Spectrum Disorder, such as aberrant social behaviors, and some social anxiety disorders. Having a known animal model for future testing could be a major boon to neurological researchers working to address these disorders, Henry says.

“It is exciting and encouraging to see what can be learned about social interactions that span the animal kingdom and, by relation, understand the diverse and complex social interactions in ‘normal’ humans and humans with social disorders,” he says.

Future experimentation with octopuses could provide valuable insight, but neuro-pharmacologist Alli Feduccia of the Multidisciplinary Association for Psychedelic Studies in Santa Cruz, California, advises proceeding with caution.

“While [an octopus] is not a model of autism, it is a model of social anxiety,” says Feduccia, whose team recently published the first clinical trial using MDMA to relieve symptoms of social limitation in autistic adults. “I don’t know if [anxiety] goes as far as being a disorder in octopuses, but they do like to be alone. I don’t know what we will learn about humans with this model of MDMA that we don’t know already.”

Feduccia reiterates that the study’s biggest finding is that we share something in common with these marine oddballs. The seemingly alien creatures are not so different from us after all, and for Dölen, that’s the heart—and if you’re an octopus, the hearts—of this research.

“As human beings we care a lot about where we came from and what our ancestors looked like, [and] in some sense this is giving us a window into where we came from,” she says. “We’ve been social for a really long time.”