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Earlier this year, many suspected octopuses of being aliens. The conspiracy theorizing began when a team of scientists sequenced the eight-armed creature’s genome and declared it “utterly different from all other animals.” However, it was quickly deemed that, despite their funky DNA, octopuses are not from another world. The thought was not without measure, however, as the highly intelligent, multi-armed invertebrates continue to surprise scientists with their bizarre behavior. In particular, their sleep patterns have caused scientists to realign their views on what they know about rest.

Octopuses — and fellow cephalopods such as squid and cuttlefish — seem to stymie traditional evolutionary behavior. While invertebrates, they have massive brains relative to their size. They also display the kind of cognitive function once considered exclusive to higher vertebrates: they use simple tools, appear to form close-knit relationships with their kin and solve puzzles. 

Just watch this clever creature easily escape this closed jar.

For years, scientists believed that, since they’re invertebrates, the eight-limbed creatures didn’t have the mental capacity to achieve slow wave sleep. In the field, scientists would notice octopuses twitching and figured it meant they rarely slept at all. Instead, they thought the creatures were, like many, in a perpetual state of high alert in case predators were lurking.

However, researcher Roger Anderson found out that these ancient creatures fooled us all. In a Discover Magazine article, Anderson theorized that octopouses do in fact sleep in cycles. During that state, “their eyes glaze over, their breathing turns slow and shallow, they don't respond to light taps, and a male will let his delicate ligula — the sex organ at the tip of one arm — dangle perilously.” 

Research did in fact favor the theory that octopuses actually sleep more like humans. As we sleep, we vertebrates have distinct, wavy brainwave patterns. Although octopuses’ brainwaves are seen as a jagged pattern, it was determined that they experience similar sleep cycles — including eye-twitching REM sleep. It even sometimes changed color. That state of hyper-vigilance state was actually the twitching associated with rapid eye movement.

And scientists are constantly surprised by the creatures' behavior. 

In one relevant example of how our knowledge of the octopus’ sleep patterns are changing, Canadian comparative psychologist Jennifer Mather took to the waters of Bermuda to examine the common Atlantic octopus. There, she witnessed a specimen emerge from its house after eating a meal of four crabs, collect rocks in its tentacles and pile them in front of its house to take a siesta in safety. That's not the mark of a creature who sleeps without purpose. 

Between their DNA and dozing habits, octopuses are sure to puzzle scientists for decades to come. And that's just fine. The cephalpods are clever enough to keep their audience wanting more.