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Octopi: The New Kings of Disguise

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by Ed Yong

Photo by Michael Nolan / SplashdownDirect / Rex USA.

At the age of 21, snorkeling the clear, blue waters off Panama’s coast, Roger Hanlon caught his first glimpse of it. As he scanned for vibrant sea life, his tall frame cast a shadow on an octopus below. Sensing danger, the creature blasted water at Hanlon before dashing off, its skin changing colors as it moved. First terrified, then intrigued, Hanlon chased the 1-pound mollusk for the next 20 minutes. “I just marveled at its changeable camouflage,” he says. “It moved along, fully exposed but really hard to see.”

Since then, Hanlon has spent more than 30 years tracking and filming thousands of octopuses, squid, and cuttlefish—collectively known as cephalopods—as they change the pattern, color, and even texture of their skin in waters around the globe. A senior researcher at the Marine Biological Laboratory in Woods Hole, Mass., Hanlon knows cephalopods’ tricks better than anyone else in the world. And now, he’s on the cusp of unlocking the secret of their chameleon-like talents.

Armed with a $6 million grant from the U.S. Office of Naval Research, Hanlon and a team of engineers are building technology that will duplicate the cephalopods’ spectacular abilities. What could humans do with such talent? Imagine pattern-shifting clothes or cars that regulate their temperature by changing color. Thanks to Hanlon’s work, that’s just around the corner.

The New Chameleons

As disappearing acts go, cephalopods are unparalleled. Instead of settling for one mode of camouflage, they’ve mastered just about all of them. This is in part because they live in the planet’s most visually diverse environments—coral reefs and kelp forests—where patterns of light and color vary more than even in tropical rainforests. But Hanlon suspects that their abilities evolved not because they have so much to hide against but because there’s so much to hide from.

“Cephalopods, being soft-bodied and nutritious, occupy that point in the food web that’s right in the middle,” says Hanlon. The creatures find themselves on the menu of virtually every ocean predator: birds, fish, dolphins, and plenty of others. And each of these predators has different visual powers. Some see ultraviolet light. Others detect polarized light. Still others have flawless nighttime vision. Cephalopods effectively have to hide from the most sophisticated eyes in the world. “We’re not looking at something humdrum that works against one or two predators in one or two habitats,” says Hanlon. Instead, cephalopods are wielders of über-camouflage: an omni-disguise that’s evolved to fool every possible prying eye.

Speed also matters. In just over two seconds, an octopus can completely transform from the stony, rugged hues of a rock to a smooth, ghostly white. But how does it access such a wide palette? The trick is in the skin: An octopus can expand and contract sacs of red and yellow pigments called chromatophores, which are dotted across its body but have uninterrupted nerve connections to its brain. Upon receiving a signal from those nerves, radial muscles pull outward on a sac, stretching from an inconspicuous speck to a flat, colorful disc. Meanwhile, underlying cells called iridophores have the ability to reflect cooler blues and greens from ambient light. Between these layers, the animals have the entire spectrum covered.

But camouflage for a cephalopod is about more than just a color scheme—the creatures can change shape too. Cuttlefish splay and ruche their arms, protruding small studs from their skin, until they resemble floating algae. Some octopuses transform themselves into rolling rocks or coconuts by walking on two arms while wrapping the others around themselves. And the most talented charlatan of them all, the mimic octopus, seems to imitate an entire toxic menagerie. Pulling its arms back into a flat leaf, it suddenly resembles a flounder. By hiding six arms and its head in a burrow, it passes for a sea snake.

The cephalopods are so good at hiding that Hanlon’s first challenge is finding them. Throughout the years, he’s perfected the art. He tracks some species by looking for the graveyards of their prey. “Octopuses are litterbugs,” he says. “They’ll gather crabs and clams and leave the shells around.” Once he’s marked a den, Hanlon will pull an early shift, staking out the territory until the owner comes back. “It’s very labor-intensive. I’ve gone through a lot of volunteer divers who spend their morning watching a stupid rock.”

Yet for Hanlon, the work is gratifying. He knows cephalopods could be the key to understanding camouflage in all species. And the creatures themselves still dazzle him. “They’re charismatic, interesting, and colorful, and they do things we don’t expect. That’s fun science.”

Finding a Pattern

Back in the lab, Hanlon and his team have placed cuttlefish on checkerboards, sand beds, and other surfaces of different patterns and colors, conducting plenty of analysis along the way. But of all the cephalopods’ abilities, Hanlon thinks that replicating background is the most important. While many visual predators have poor color vision, almost all of them are good at detecting mismatched patterns.

And for all the astonishingly varied backgrounds that cephalopods can mimic, Hanlon believes that their disguises come in just a few basic types. In 1998, he accumulated hundreds of cuttlefish photos and started sorting them into piles based on pattern. “Much to my surprise, I came up with just a few piles,” he says. More than a decade, thousands of photos, and several quantitative measurements later, “the same three pattern templates hold,” he says. In uniform mode, the animal’s entire body takes on the same uniform brightness, like a sandy floor. In mottled mode, the body displays small repetitive patches of light and dark, like a gravel bed. And in disruptive mode, it has bigger patches that sharply contrast with each other, presented in different scales, shapes, and orientations. This variation helps to break up the animal’s recognizable outline. Of course, there are plenty of minor differences, but it’s the low total number of patterns that intrigues him. “I don’t care if it’s two or 10, but I’m sure it’s not 55 or 1,000. That’s already a counterintuitive notion.”

Hanlon’s three-pattern hypothesis also explains how cephalopods can disappear from view within tenths of a second without needing “a brain the size of a Volkswagen,” since the animals can simply rely on one rule for each pattern type. For example, Hanlon’s team has shown that a cuttlefish will don its disruptive suit if it sees a light patch that’s sharply contrasted to the darkness around it. Rather than parsing through all the visual information surrounding it, the cuttlefish susses out a few key clues to determine the dress code.

But perhaps the strangest thing about their ability is that, while cephalopods can mimic the entire spectrum of colors, they themselves are color-blind. In 2008, Hanlon, along with fellow researchers Lydia Mathger and Steven Roberts, found a big clue: light-sensitive pigments called opsins dotted all over the creatures’ skin. Opsins are typically found in eyes and are essential for vision. The discovery raises the tantalizing possibility that these animals could sense light in a novel way. “Maybe there’s sensing going on in the skin, independently of the central nervous system,” says Hanlon.

As Hanlon probes these skin pigments further, his collaborators will take the biological principles and give them an engineering spin. Their plan is to develop materials that can sense light and change color with the same speed and efficiency as a living cephalopod—by using distributed light sensors that can coordinate brightness and color without needing a central “brain,” or processing unit. Understanding how the living animals do it will be critical. “The engineers are invariably astounded by the weirdness of it all, but once they get some numbers, they’re impressed by how efficient [the ability] is,” Hanlon says.

The potential applications are as diverse as they are exciting. “Think about townships with water towers or industrial plants with chemicals in holding tanks,” says Hanlon. “When they heat up or become too cold, they become a problem.” A light-sensitive coating that could change color to control how much heat it absorbs would solve that problem. Our favorite gizmos could benefit too. A squid’s skin is just as vibrant and dynamic as an iPhone but runs on far less energy. “If we work out how biological systems handle light and add that to our technology,” says Hanlon, “the efficiency’s going to go right up.”

This story originally appeared in mental_floss magazine. For a free issue, go download our iPad app! Or the new Android app! Or get a free issue of mental_floss magazine via mail.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Sponsor Content: BarkBox
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8 Common Dog Behaviors, Decoded
May 25, 2017
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Dogs are a lot more complicated than we give them credit for. As a result, sometimes things get lost in translation. We’ve yet to invent a dog-to-English translator, but there are certain behaviors you can learn to read in order to better understand what your dog is trying to tell you. The more tuned-in you are to your dog’s emotions, the better you’ll be able to respond—whether that means giving her some space or welcoming a wet, slobbery kiss. 

1. What you’ll see: Your dog is standing with his legs and body relaxed and tail low. His ears are up, but not pointed forward. His mouth is slightly open, he’s panting lightly, and his tongue is loose. His eyes? Soft or maybe slightly squinty from getting his smile on.

What it means: “Hey there, friend!” Your pup is in a calm, relaxed state. He’s open to mingling, which means you can feel comfortable letting friends say hi.

2. What you’ll see: Your dog is standing with her body leaning forward. Her ears are erect and angled forward—or have at least perked up if they’re floppy—and her mouth is closed. Her tail might be sticking out horizontally or sticking straight up and wagging slightly.

What it means: “Hark! Who goes there?!” Something caught your pup’s attention and now she’s on high alert, trying to discern whether or not the person, animal, or situation is a threat. She’ll likely stay on guard until she feels safe or becomes distracted.

3. What you’ll see: Your dog is standing, leaning slightly forward. His body and legs are tense, and his hackles—those hairs along his back and neck—are raised. His tail is stiff and twitching, not swooping playfully. His mouth is open, teeth are exposed, and he may be snarling, snapping, or barking excessively.

What it means: “Don’t mess with me!” This dog is asserting his social dominance and letting others know that he might attack if they don’t defer accordingly. A dog in this stance could be either offensively aggressive or defensively aggressive. If you encounter a dog in this state, play it safe and back away slowly without making eye contact.

4. What you’ll see: As another dog approaches, your dog lies down on his back with his tail tucked in between his legs. His paws are tucked in too, his ears are flat, and he isn’t making direct eye contact with the other dog standing over him.

What it means: “I come in peace!” Your pooch is displaying signs of submission to a more dominant dog, conveying total surrender to avoid physical confrontation. Other, less obvious, signs of submission include ears that are flattened back against the head, an avoidance of eye contact, a tongue flick, and bared teeth. Yup—a dog might bare his teeth while still being submissive, but they’ll likely be clenched together, the lips opened horizontally rather than curled up to show the front canines. A submissive dog will also slink backward or inward rather than forward, which would indicate more aggressive behavior.

5. What you’ll see: Your dog is crouching with her back hunched, tail tucked, and the corner of her mouth pulled back with lips slightly curled. Her shoulders, or hackles, are raised and her ears are flattened. She’s avoiding eye contact.

What it means: “I’m scared, but will fight you if I have to.” This dog’s fight or flight instincts have been activated. It’s best to keep your distance from a dog in this emotional state because she could attack if she feels cornered.

6. What you’ll see: You’re staring at your dog, holding eye contact. Your dog looks away from you, tentatively looks back, then looks away again. After some time, he licks his chops and yawns.

What it means: “I don’t know what’s going on and it’s weirding me out.” Your dog doesn’t know what to make of the situation, but rather than nipping or barking, he’ll stick to behaviors he knows are OK, like yawning, licking his chops, or shaking as if he’s wet. You’ll want to intervene by removing whatever it is causing him discomfort—such as an overly grabby child—and giving him some space to relax.

7. What you’ll see: Your dog has her front paws bent and lowered onto the ground with her rear in the air. Her body is relaxed, loose, and wiggly, and her tail is up and wagging from side to side. She might also let out a high-pitched or impatient bark.

What it means: “What’s the hold up? Let’s play!” This classic stance, known to dog trainers and behaviorists as “the play bow,” is a sign she’s ready to let the good times roll. Get ready for a round of fetch or tug of war, or for a good long outing at the dog park.

8. What you’ll see: You’ve just gotten home from work and your dog rushes over. He can’t stop wiggling his backside, and he may even lower himself into a giant stretch, like he’s doing yoga.

What it means: “OhmygoshImsohappytoseeyou I love you so much you’re my best friend foreverandeverandever!!!!” This one’s easy: Your pup is overjoyed his BFF is back. That big stretch is something dogs don’t pull out for just anyone; they save that for the people they truly love. Show him you feel the same way with a good belly rub and a handful of his favorite treats.

The best way to say “I love you” in dog? A monthly subscription to BarkBox. Your favorite pup will get a package filled with treats, toys, and other good stuff (and in return, you’ll probably get lots of sloppy kisses). Visit BarkBox to learn more.

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