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What Spitting Cobras are Aiming For

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Make most cobras angry, and they’ll bite you and inject the bite with a dose of venom. Frighten or tick off a spitting cobra, though, and it will contract the muscles around its venom glands and “spit” it out through holes in the tips of its fangs. Right into your face. 

Spitting cobras are no slouches when it comes to marksmanship. Neurobiologist Bruce Young found this out when he put on a plastic face mask a few years ago and taunted cobras into taking more than a hundred shots at him. When he analyzed the snakes’ movements, he found that they always spit right after he made a jerky movement with his head. The snakes would turn their heads in the same direction that he’d started to move his and then start spitting. Tracking the target like this, Young wrote in his study, “gives cobras a distinct geometric advantage; even relatively large linear movements on the part of the target can be accommodated by rather modest angular movements of the cobra's head.” A burst of speed when turning their heads also lets the snakes “lead” the target a little and compensate for the time it takes for their muscles to send the venom flying. 

It’s a cool tactic, but not as easy as just biting whatever it is that needs biting. You see, spitting cobra’s venom doesn’t do anything if it just hits you on the skin or even gets in your mouth. To be of any use, the venom has to get in your eye, where it causes searing pain and can scar the corneas and leave you blind.

This has had many biologists wondering if the cobras know to shoot for the eyes and are aiming at them. Given the snakes’ accuracy when spitting and the limited targets that their venom is effective on, scientists, zookeepers and others who study and work with spitting cobras assumed they were. In 2005, researchers from the University of Bonn in Germany backed these assumptions up with an experiment. They put undergrad student Katja Tzschätzsch face-to-face with 10 different cobras and got them to spit at her hands, her face and life-sized photos of faces. Hands and still faces and photos didn’t get a rise out of the snakes, but a moving face (real and fake) did—less so when the eyes were digitally removed from the photos than when they were left intact. When the researchers looked at the traces of venom on the photos and Tzschätzsch’s facemask, they found that the different cobras hit the eyes anywhere from 80 percent to 100 percent of the time.

Now a newer study suggests that maybe the cobras aren’t so picky when choosing their targets. Guido Westhoff, a neurobiologist who worked with Young and Tzschätzsch on the previous research, revisited the question last year with another round of experiments. He and his team presented cobras with life-size, human face-shaped boards with and without different kinds of glass eyes, as well as larger and smaller fake faces and triangular boards that didn’t resemble faces. 

In 324 spitting tests, the snakes didn’t spit at the boards with eyes any more than the ones without. Also, when the eyes on the targets were moved closer together or farther apart, the snakes didn’t adjust their aim to account for the distance between them. Given a choice between a face with eyes and an eyeless one, the snakes spit at the larger target most of the time, whether it had eyes or not. 

Westhoff now thinks that cobras don’t specifically aim for the eyes, but for the center of whatever body part their tormenter puts closest to them. Often, this just happens to be the face—and it seems the snakes prefer more face-like round targets than pointy ones; they spit at those almost four times as much—and at least one eye gets hit by chance. 

What’s more, he thinks that aiming for the eyes is both unnecessary and even a bad strategy for the snakes. Cobras can spray their venom over a wider area by moving their head as they spit and spitting several times in a row, increasing their chances of hitting the eye and without requiring them to aim right at them. Shooting for eyes instead of just a face also puts a cobra at a disadvantage if it can’t clearly see or recognize eyes, like when their own eyes become cloudy while they shed their skins, or in the dark. 

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iStock // Ekaterina Minaeva
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technology
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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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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Smart Shopping
This Week's Best Amazon Deals You Can Still Get
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As a recurring feature, we share some amazing Amazon deals we’ve turned up. These items were the ones that were the most popular with our readers this week, and they’re still available.

Mental Floss has affiliate relationships with certain retailers, including Amazon, and may receive a small percentage of any sale. But we only get commission on items you buy and don’t return, so we’re only happy if you’re happy. Good luck deal hunting!

GADGETS, TOYS, AND MEDIA

Fitbit Surge Fitness Superwatch, Black, Large (US Version) for $229.94 (list price $249.95)

Brother Printer EHLL2360DW Compact Laser Printer, Duplex Printing & Wireless Networking, Refurbished for $69.99 (list price $89.99)

VicTsing Shower Speaker, Wireless Waterproof Speaker with 5W Driver, Suction Cup, Buit-in Mic, Hands-Free Speakerphone - Army Green for $18.99 (list price $24.99)

CardNinja Ultra-slim Self Adhesive Credit Card Wallet for Smartphones, Black for $6.95 (list price $12.99)

Anker Quick Charge 2.0 36W Dual USB Car Charger, PowerDrive+ 2 for Galaxy S7 / S6 / Edge / Plus, Note 5 / 4 and PowerIQ for iPhone 7 / 6s / Plus, iPad Pro / Air 2 / mini, LG, Nexus, HTC and More for $12.99 (list price $59.99)

Timex T235WY AM/FM Dual Alarm Clock Radio - White for $19.65 (list price $24.95)

Lexar JumpDrive P20 64GB USB 3.0 Flash Drive - LJDP20-64GCRBNA for $34.47 (list price $41.49)

Anker PowerLine+ Lightning Cable (6ft) Durable and Fast Charging Cable [Double Braided Nylon] for iPhone, iPad and More(White) for $13.99 (list price $39.99)

Roku Streaming Stick (3600R) - HD Streaming Player with Quad-Core Processor for $39.99 (list price $49.99)

AmazonBasics 6-Outlet Surge Protector Power Strip 2-Pack, 200 Joule - Black for $9.99 (list price $11.49)

DOSS Touch Wireless Bluetooth V4.0 Portable Speaker with HD Sound and Bass (Black) for $32.99 (list price $89.99)

Fujifilm Instax Mini Film Value Pack - 60 Images for $34.99 (list price $39.99)

Cell Phone Camera Lens - TURATA 2 in 1 Professional HD Camera Lens Kit 0.45X Super Wide Angle & 12.5X Macro Lens for iPhone7 6s 6s plus 6 plus 5s & Most Smartphone, Tablet for $11.98 (list price $30.99)

Sades Over-Ear Stereo Bass Gaming Headphone with Noise Isolation Microphone for Xbox One PC PS4 Laptop Phone for $23.99 (list price $39.99)

InkoTimes Bamboo Charging Station Dock Organizer for Apple Watch, iPhone, iPad, Universal Cell Phones and Tablets, Compatiable with Anker, RAVPower, PowerAdd, 4/5/6-Port USB Charger for $35.99 (list price $59.99)

KITCHEN

Aicok Juicer Juice Extractor High Speed for Fruit and Vegetables Dual Speed Setting Centrifugal Fruit Machine Powerful 400 Watt with Juice Jug and Cleaning Brush, Premium Food Grade Stainless Steel for $48.99 (list price $99.99)

Rabbit Wine Opener Corkscrew BEST Wine Bottle Opener - 7 Piece Rabbit Ear Bundle with Stand, Bottle Plug, Wine Aerator, Drip Ring, Foil Cutter & EXTRA Teflon Spiral + Wooden Box Perfect Gift Set for $35.00 (list price $69.99)

Magic Bullet Blender, Small, Silver, 11 Piece Set for $34.00 (list price $39.99)

ThermoPro TP03A Digital Food Cooking Thermometer Instant Read Meat Thermometer for Kitchen BBQ Grill Smoker for $10.49 (list price $29.99)

Etekcity Digital Kitchen Scale Multifunction Food Scale, 11 lb 5 kg, Silver, Stainless Steel (Batteries Included) for $13.98 (list price $39.99)

Ado Glo Kitchen Shears - Stainless Steel Multi-Function Kitchen Scissors with Sharp Blade - Professional Poultry Shears for $12.95 (list price $34.99)

ISSIKI JAPAN Professional 8 Inch Chef's Knife, Gyutou Knife, Kitchen Knife, High Carbon Stainless Steel, Sharp Cutlery, Ergonomic Handle for $24.99 (list price $125.00)

12-Pack KEURIG Compatible Water Filters by K&J - Universal Fit (NOT CUISINART) Keurig Compatible Filters - Replacement Charcoal Water Filters for Keurig 2.0 (and older) Coffee Machines for $9.95 (list price $19.95)

Hamilton Beach 22910 Brushed Stainless Steel 2-Slice Toaster for $9.24 (list price $24.99)

Spiralizer 5-Blade Vegetable Slicer, Strongest-and-Heaviest Duty, Best Veggie Pasta & Spaghetti Maker for Low Carb/Paleo/Gluten-Free Meals, With 3 Exclusive Recipe eBooks for $29.99 (list price $49.99)

Stainless Steel Mixing Bowls by Finedine (Set of 6) Polished Mirror Finish Nesting Bowls, ¾ - 1.5 - 3 - 4 - 5 - 8 Quart - Cooking Supplies for $22.95 (list price $39.95)

Hiware 12-piece Good Stainless Steel Dinner Forks Cutlery Set, 8 Inches for $15.59 (list price $22.00)

HOME

Furhaven Orthopedic Mattress Pet Bed, Large, Cream, for Dogs and Cats for $25.49 (list price $30.44)

12 Air Plant Variety Pack - Bulk Assorted Species of Live Tillandsia House Plants for Sale - Wholesale Indoor Terrarium Air Plants by Aquatic Arts for $22.99 (list price $25.08)

Estilo 1 gallon Glass Mason Jar Double Beverage Drink Dispenser On Metal Stand With Leak Free Spigot, Clear for $27.98 (list price $31.88)

Poly and Bark Ralston Writing Desk - Standard Height - in Ash Grey for $49.99 (list price $55.99)

Outsunny 3 Person Canopy Porch Swing - Black for $132.67 (list price $99.99)

Sterilite 25306P01 3 Drawer Wide Weave Tower, Espresso Frame & Drawers w/ Driftwood Handles, 1-Pack for $19.83 (list price $22.44)

AmazonBasics Mid-Back Mesh Chair for $49.58 (list price $64.99)

Mpow LED Solar light, Bright Security Lighting Outdoor Motion Sensor Lighting for Garden, Patio for $14.99 (list price $19.99)

HOMFA Fashion Heavy Duty Garment Rack with Shelves 3-Tier Shoes Rack,Coat Rack Hooks,Clothes Rack with Hanger Bar (Black) for $49.99 (list price $110.99)

Premium 8 Piece Towel Set (Grey); 2 Bath Towels, 2 Hand Towels and 4 Washcloths - Cotton - Machine Washable, Hotel Quality, Super Soft and Highly Absorbent by Utopia Towels for $25.99 (list price $43.99)

HEALTH AND BEAUTY

VicTsing 300ml Cool Mist Humidifier Ultrasonic Aroma Essential Oil Diffuser for Office Home Bedroom Living Room Study Yoga Spa - Wood Grain for $49.99 (list price $29.99)

Nerdwax Stop Slipping Glasses as Seen on Shark Tank for $12.99 (list price $14.99)

Redken Short Sculpt 19 Touchable Texturizing Gel, 3.4 Ounce for $12.46 (list price $20.00)

Oak Leaf 7X Magnification LED Lighted Makeup Mirror,Bright Shaving Bathroom Vanity Mirror with Strong Suction Cup,Touch-Activated,Rotates 360 Degrees,Daylight Color,Battery Operated for $19.99 (list price $59.99)

BraceUP Stabilizing Lumbar Lower Back Brace and Support Belt with Dual Adjustable Straps and Breathable Mesh Panels (S/M) for $23.99 (list price $45.98)

Brightdeal Replacement Brush Heads for Philips Sonicare Toothbrush E Series HX7022/66, Essence, Xtreme, Elite and Advance (6-pack) for $19.99 (list price $25.99)

Philips Sonicare Essence Sonic Electric Rechargeable Toothbrush, White for $24.95 (list price $49.99)

Swiffer Duster Refills, Unscented Dusters Refill, 20 count for $13.97 (list price $15.99)

Braun Series 9-9095cc Wet and Dry Foil Shaver for Men with Cleaning Center, Electric Men's Razor, Razors, Shavers, Cordless Shaving System for $299.99 (list price $499.99)

Johnson's 24 Hr Moisturizing Wash Soft Body Lotion 12 fl oz (6 pack) for $26.99 (list price $29.99)

Germ-X 1000042965 Moisturizing Hand Sanitizer Lotion 4 oz. (Pack of 12) for $38.53 (list price $55.28)

Radha Beauty Natural Therapeutic Frankincense Essential Oil, 4 oz. for $16.95 (list price $49.99)

FHI Brands Stylus Thermal Styling Brush, Black for $79.99 (list price $99.99)

Thayers Alcohol-free Rose Petal Witch Hazel with Aloe Vera, 12 oz for $10.51 (list price $19.95)

OFFICE, SCHOOL, AND CRAFTS

AmazonBasics Wireless Presenter for $21.00 (list price $24.99)

Anycolor 3 Pack Compatible Brother M221 M-K221 MK221 M Tape Black on White Label Tape for Brother P Touch Label Maker PT-90 PT-M95 PT-70BM PT-70 PT-65 PT-85 PT-45 (3/8" x 26.2' 9m x 8m) for $32.49 (list price $32.49)

EXPO Low-Odor Dry Erase Markers, Fine Tip, Assorted Colors, 8-Count for $7.37 (list price $11.49)

HIRALIY CH019 Aluminum Portable Laptop Stand for 13" & Smaller Laptops/Notebooks/ /Tablets (Grey) for $29.99 (list price $49.99)

Thick Classic Notebook with Pen Loop - Lemome Wide Ruled Hardcover Journal with Pocket to Write in + Page Dividers Gifts, Banded, Large, 180 Pages, 8.4 x 5.7 in for $14.99 (list price $25.99)

Clipboards (Set of 10) by Office Solutions Direct! Low Profile Clip Standard A4 Letter Size clipboard for $12.88 (list price $29.95)

VANRA Metal Mesh Desktop File Sorter Organizer Desk Tray Organize with 3 Letter Trays and 2 Vertical Upright Sections, Black for $33.98 (list price $68.80)

Paper Mate Profile Retractable Ballpoint Pens, Bold (1.4mm), Assorted Colors, 12 Count for $6.69 (list price $17.09)

Five Star Spiral Notebook, 3 Subject, College Ruled, 150 Sheets, Black, Cobalt Blue, Red, 3 PACK (73393) for $12.87 (list price $29.99)

HP Paper, Office Ultra White, 20lb, 8.5 x 11, 3 Hole Punch , 92 Bright, 500 Sheets / 1 Ream (113102R), Made In The USA for $4.01 (list price $7.01)

Sharpie Accent Retractable Highlighters, Chisel Tip, Assorted Colors, 8-Count for $7.54 (list price $8.38)

U Brands Contempo Magnetic Monthly Calendar Dry Erase Board, 11 x 14 Inches, White Frame for $5.73 (list price $8.99)

EXPO Low-Odor Dry Erase Markers, Chisel Tip, Fashion Colors, 8-Count for $4.94 (list price $8.92)

Board Dudes 18" x 22" Magnetic Dry Erase/Cork Combo Board (CYH10) for $13.19 (list price $20.23)

Electric Pencil Sharpener - Battery Operated (No Cord) - Ideal For No. 2 and Colored Pencils (Drawing, Coloring) - Small and Durable - Kid Friendly - Artist , Students , and Professionals for $16.99 (list price $34.99)

Sargent Art 36-1012 36 Count Premium Pink Eraser Best Buy Pack for $4.99 (list price $20.29)

OUTDOORS, GARDEN, AND SPORTS

SHINE HAI Double Camping Hammock, Portable Lightweight Parachute Nylon Garden Hammock, Two Persons Bed for Backpacking, Camping, Travel, Beach, Yard for $23.99 (list price $139.99)

LUXUR Casual Foldable Nylon Backpack Hiking Sport Durable Lightweight Hand Bag 33L for Men and Women Rose Red for $8.99 (list price $35.99)

Polar Bottle Insulated Water Bottle (24-Ounce) (Starburst) for $8.92 (list price $11.99)

KT TAPE PRO Kinesiology Sports Tape, 20 Precut 10in Strips, 100% Synthetic, Water Resistant, Breathable, Videos, Team USA Olympic Edition, Black for $9.99 (list price $14.99)

Polar H7 Bluetooth Heart Rate Sensor & Fitness Tracker (Black, Medium/XX-Large) for $41.12 (list price $58.49)

TaylorMade 2016 Tour Preferred Golf Balls (1 Dozen) for $24.99 (list price $39.00)

JOOLA Conversion Table Tennis Top with Foam Backing and Net Set for $308.39 (list price $374.99)

Homitt 2 Way Y Hose Connector, Garden Hose Splitter with Comfortable Rubberized Grip for Easy Garden Life for $11.99 (list price $29.99)

BLACK+DECKER LST300 12-Inch Lithium Trimmer / Edger, 20-volt for $55.30 (list price $64.99)

Caravan Sports Infinity Zero Gravity Chair, Beige for $36.23 (list price $79.99)

TOOLS

Schlage FE595 CAM 619 ACC Camelot Keypad Entry with Flex-Lock and Accent Levers, Satin Nickel for $87.73 (list price $109.67)

Etekcity 3 Pack Portable Outdoor LED Lantern with 9 AA Batteries - Camping Friendly (Black, Collapsible) for $17.99 (list price $50.99)

First Alert AF400-2 Tundra Fire Extinguisher Aerosol Spray Twin Pack for $22.49 (list price $28.92)

Maxcraft 60626 8-oz. Stubby Claw Hammer for $10.89 (list price $12.48)

Coleman Cable 02309 16/3 Vinyl Outdoor Extension Cord, Orange, 100-Feet for $22.92 (list price $26.30)

BLENDX 7mm to 19mm Ratchet Universal Sockets Metric Wrench Power Drill Adapter Set - Professional Repair Tools for $9.99 (list price $15.99)

First Alert SCO5CN Battery Operated Combination Carbon Monoxide/Smoke Alarm for $31.24 (list price $33.93)

URPOWER Tactical Flashlight Super Bright CREE LED Flashlight Zoomable Tactical Flashlight Rainproof Lighting Lamp Torch -with Rechargeable 18650 2800mAh Battery -For Cycling Hiking Camping Emergency for $10.99 (list price $39.99)

Custom Leathercraft 1100 Multi-Purpose Clip-on Zippered Poly Bags for $6.72 (list price $7.82)

Campbell Hausfeld 17-Piece Air Tool and Accessory Kit (MP284701AV) for $11.78 (list price $17.07)

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