Giving animals drugs sounds like a cruel activity, perhaps something you'd expect from delinquent teenagers looking for a cheap laugh at the expense of another creature. But, it turns out, giving octopuses psychoactive drugs can actually have some scientific value.

That's what U.S. researchers discovered after a designed experiment to see how California two-spot octopuses (Octopus bimaculoides) reacted to being given MDMA, better known as the drug ecstasy. Surprisingly, the animals behaved much like humans do under the influence of the drug, with a lot of hugging and cuddles, according to a media release.

The research was also performed according to guidelines laid out in the Animal Welfare Act, so despite their strange trip, the octopuses went on to live perfectly healthy, cephalopod lives.

The study was also approved on more than a whim. After the genome of the California two-spot octopus was recently sequenced and published, scientists noticed some curious similarities between human and octopus brains, even though there are over 500 million years of evolution that separates us from these intelligent invertebrates. Namely, we seem to share a transporter that binds the neurotransmitter serotonin.

For humans, serotonin plays an important role in mood regulation, feelings of happiness and well being, as well as depression. Scientists wondered if it might also play a similar role in octopus behavior. And one of the easiest ways to test this is to introduce MDMA, a drug known to increase the activity of serotonin.

"Despite anatomical differences between octopus and human brain, we've shown that there are molecular similarities in the serotonin transporter gene," said neuroscientist Gül Dölen of Johns Hopkins University. "These molecular similarities are sufficient to enable MDMA to induce prosocial behaviors in octopuses."

Humans become more empathetic when taking ecstasy; it's also known as the "happy drug" because it generates feelings of euphoria, especially from touching. It's no different for octopuses, apparently.

Researchers observed as the ecstasy-influenced cephalopods spent a lot of time embracing one another. And interestingly, this is a species that is usually thought of as more solitary.

The study tells us a lot about the evolutionary roots of serotonergic signaling in the regulation of social behaviors. It's remarkable to think that behaviors and social capacities typically thought of as rather complex might go back over 500 million years, and even be more widespread in the animal kingdom than we ever thought possible.

It's also somewhat comforting to know that this element of cognition, our friendlier and more affectionate social capacities, might be translatable across wide species barriers. In a way, it brings us all a little bit closer.

Scientists gave octopuses ecstasy, and there was a lot of cuddling
Study of California two-spot octopuses (Octopus bimaculoides) hows surprising similarities between the biochemistry of humans and octopuses.