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Some Bats Call “Dibs” on Food

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In my seven-sibling family, “dibs” is the most frequently heard phrase at holiday meals. Everyone wants to lay claim to the turkey drumstick or the end piece on the ham or the last (several) beer(s) in the fridge. And it’s not just me and my brothers and sisters that warn each other to back off from our food: Scientists now think that bats do it, too. 

Researchers at the University of Maryland were examining audio recordings of big brown bats (Eptesicus fuscus) when they noticed that some of the noises the animals made were a little weird. They were unlike the sounds that bats usually use for echolocation, and turned out to be social or communicative calls, the bat version of conversation. 

One of the calls consisted of three or four long, low downward sweeps through a range of frequencies and then a few short, buzz-like calls. The “frequency-modulated bout” (FMB), as the researchers dubbed it, only seemed to be made when the bats were hunting for food. 

To learn more about the FMBs, the researchers, led by biologist Genevieve Wright, dangled a mealworm in a lab enclosure and let some bats have at it, either individually or in pairs, while they recorded things with high-speed video and audio equipment. 

The recordings revealed that only male bats emitted FMBs, and only when they were hunting with another bat. Once one bat produced an FMB, the other one quickly changed its behavior, breaking its flight path toward the food and increasing the distance between itself and the calling bat. The bat that made the noise then claimed the prey for itself. When both bats produced FMBs, the one that emitted more of the calls usually nabbed the mealworm. 

All this suggests that the FMBs have a repellent effect on nearby bats, and are the animals’ way of calling dibs on a prey item and saying “hey, that one’s mine, back off!”

The researchers are left with a nagging question, though. Why do only male bats call dibs? It might be that females don’t need to because they usually hunt alongside related bats and roost-mates, while males often forage with other, unrelated males and there is stronger competition for prey. The researchers also say its possible that only males make the FMBs because they’re related to a male-specific mating call. Even though Wright’s team only examined the calls outside of mating season, other researchers have described calls similar to the FMB being used during mating to assert control over a contested mate. 

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iStock // Ekaterina Minaeva
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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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iStock
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Why Your iPhone Doesn't Always Show You the 'Decline Call' Button
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iStock

When you get an incoming call to your iPhone, the options that light up your screen aren't always the same. Sometimes you have the option to decline a call, and sometimes you only see a slider that allows you to answer, without an option to send the caller straight to voicemail. Why the difference?

A while back, Business Insider tracked down the answer to this conundrum of modern communication, and the answer turns out to be fairly simple.

If you get a call while your phone is locked, you’ll see the "slide to answer" button. In order to decline the call, you have to double-tap the power button on the top of the phone.

If your phone is unlocked, however, the screen that appears during an incoming call is different. You’ll see the two buttons, "accept" or "decline."

Either way, you get the options to set a reminder to call that person back or to immediately send them a text message. ("Dad, stop calling me at work, it’s 9 a.m.!")

[h/t Business Insider]

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