字幕列表 影片播放 列印英文字幕 Hi, this is Kate from MinuteEarth with, uh, hands. Anyway, when I want to write, flip a pancake, or take adorable hyena pictures, like most people, I use my right hand. Because despite being a near-mirror image of my right, my left hand is *terrible* at this stuff. Lots of other animals also have a so-called "preferred" side. Gorillas generally use their right hand for tasks requiring dexterity, while orangutans use their left. Many parrots hold seeds with their left foot. And Brazilian spitting spiders tend to favor their left fore-legs while hunting. And sure, it's weird that some animals prefer their left and some their right, but what's even weirder is why we have a preferred side at all. Perhaps a hand-ier way to think about it is if having one "good" side is good, why don't we have two? It likely comes down to efficiency. Most animals have brains with two largely-independent sides that perform somewhat different functions and control different - and, weirdly - opposite sides of our bodies. Like, when I write my name, neurons in the left side of my brain send electrical signals to neurons in my right hand to tell it what to do. But building and operating that neural circuit takes a lot of time and a lot of energy - and training that limb to write decently takes even more. To write decently with my left hand, because of the quirky two-sidedness of our brains, I'd need an entirely different circuit, which would take a ton more time and energy to build, operate, and train. Instead, it's much more efficient to rely on a single circuit for writing. What's more, the more I use that circuit, the more I reinforce the neural connections from the brain to my right hand, making that hand even... well... handier, and the more likely I am to use it for other jobs. Voilà - handedness. This efficiency explanation is still somewhat theoretical, but evidence from all sorts of animals shows that having a preferred side can provide an advantage. When scientists gave a food-finding test to parrots, some of whom had a strong side preference and some didn't - the strongly-sided birds did twice as well. What's more, when the task got harder and the birds had to use a series of coordinated motions to get a snack hanging from a string, the strongly-sided birds were way better at figuring out a clever solution. And look, during this more complicated task, the "un-preferred" side had something important to do too, just like how my left hand holds and steadies the paper when I'm writing, or the camera when I'm snapping a picture. These jobs are often - literally - supporting roles, but they, too, require circuitry to perform, and training to perform well. So, maybe our so-called "weaker" side isn't actually weak after all; it's just optimized for different jobs. Without it, we wouldn't be able to hammer in a nail, play the guitar, catch and throw a baseball, perform heart surgery, or deftly wield a sword and shield. Of course, there's that question of why I - along with most humans - would swing a sword with my right hand, while far fewer would choose their left. But that's a question for another video, as this one is already out of hand. The human body is really strange - we could go on and on about it. And we actually have: We made MinuteBody, an entire series of videos about the weird workings of, well, us. You can check out the first season exclusively on Nebula, a platform built by independent education-y creators like us as a place to experiment and try out new ideas. And now CuriosityStream - a documentary streaming service that loves supporting creators - has teamed up with Nebula to launch the second season of MinuteBody. The newest episode comes out today! As part of our partnership, when you sign up for CuriosityStream at curiositystream.com/MinuteEarth, you'll also get Nebula for free. So, for just fifteen bucks a year, you'll not only get access to CuriosityStream's huge library of high-quality content like "What Animals See," you'll also get free access to tons of creative stuff on Nebula from the folks behind Real Engineering, Wendover, Tom Scott - and all new episodes of MinuteBody. Come check it out!