"After MDMA, they were essentially hugging", Dolen told NPR, adding that the dosed octopuses were "really just much more relaxed in posture, and using a lot more of their body to interact with the other octopus".
Upon being given lower doses, though, the octopuses demonstrated major behavioral changes, getting closer to each other and even touching each other.
"These molecular similarities are sufficient to enable MDMA to induce prosocial behaviours in octopuses".
The eight-legged invertebrates are separated from humans by more than 500 million years of evolution.
Researchers Eric Edsinger, Ph.D., and Gül Dölen, M.D., Ph.D. had a closer look at the genomic sequence of the California two-spot octopus and found that they and humans have almost identical genomic codes for the transporter that binds serotonin, a mood regulator, to the neuron's membrane. Serotonin plays a role in mood regulation, feelings of happiness and wellbeing, as well as depression - and its activity is increased by MDMA.
As it turns out, they may be a little more social than thought, especially given a bit of neurochemical help. One was empty, one had a plastic action figure underneath a cage, and another had a female or male laboratory-bred octopus under a cage. But when the "high" octopuses were dropped in the chamber they actively sought physical contact with the caged male. The animals absorbed it for a half hour and then were placed in a sort of multi-room chamber.
Octopuses have a reputation for being anti-social - except when they're mating - to the extent that scientists who study them have to house them separately so they don't kill and eat each other.
"It's not just quantitatively more time, but qualitative", Dölen said in a statement.
That said, researchers note that the results are still preliminary given the small sample size, and that further research is needed before octopuses can be used as models for brain research. The team adhered to guidelines as per the Animal Welfare Act, and afterwards the animals returned to their tanks in Woods Hole Oceanographic Institute in MA.