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  • [♪ INTRO]

  • It was a dark and stormy night, and the SciShow team was working late into the night on the newest episode.

  • As they toiled late into the evening, they started to noticepeculiar things.

  • There were sounds, was it a voice?

  • And the shadows flitting just out of view.

  • It was then they finally came face to face with the legendary Ghost of SciShow!

  • *Thunder* *maniacal laughter*

  • I'm just kidding.

  • But who doesn't love a good ghost story?

  • If you talk to the caretakers of old buildings, or hop onto any number of subreddits,

  • you're sure to find countless stories of personal run-ins with a spook.

  • And encountering a ghost, whether it's in an old building, your bedroom, or in the SciShow office,

  • does sound truly terrifying.

  • So, perhaps you can take comfort in the fact that these encounters can be explained by natural phenomena:

  • nosuper-” prefix necessary.

  • And a lot of it actually has to do with our brains and how they interpret the world around us.

  • If we want to talk about explanations for seeing ghosts,

  • we should start by talking about our eyes.

  • Pretty much every ghost story happens at night or in a dark place,

  • and that's probably not a coincidence.

  • Many ghost sightings are brief glimpses of something just at the edge of a person's field of vision.

  • Then, they look to see what it was, but it's gone!

  • And that kind of sighting can probably be chalked up to the way human peripheral vision works.

  • You see, your ability to detect color and resolve detail drops off considerably at the edge of your visual field.

  • But, your ability to detect motion actually increases.

  • That's because the periphery of your retina has fewer cones,

  • the light-sensing cells that excel at detecting color and shape,

  • and more rods, which are better at detecting motion.

  • So, especially in low-light and/or high-spook conditions,

  • it's easy to notice motion out of the corner of your eye without clearly making out what's actually moving.

  • Plus, all of your senses can be heightened when you're on alert,

  • which increases the likelihood you'll be frightened by otherwise mundane visible stimuli.

  • So if you just catch something moving out of the corner of your eye,

  • only to find nothing unusual there when you look,

  • it probably wasn't a supernatural being.

  • It's much more likely that the mechanics of your eyeballs made something ordinary seem extraordinary

  • than it is that a ghost crept past and then vanished.

  • One of the most common devices in a paranormal investigator's toolkit is the humble audio recorder.

  • They use it to pick up EVPs, or Electronic Voice Phenomenon...s…

  • it doesn't pluralize quite right when you spell it out.

  • Anyhow, the idea is that you can hit record, ask questions to a room,

  • and then hear vocal responses in the audio when you play it back.

  • And that's totally true.

  • It's just that those vocal responses aren't generated by ghosts, they're generated by your brain.

  • Another way our brains can trick us is pareidolia:

  • our tendency to find familiar patterns even where none exist.

  • We've talked about this before in the context of seeing faces in rocks or toast.

  • That happens because our primate brains evolved to quickly recognize one another,

  • and that ability comes with the side effect of also recognizing familiar forms

  • in otherwise random patterns.

  • Turns out this isn't just a visual thing.

  • We're so keen on recognizing other humans that we often hear human voices that aren't really there.

  • This is what's known as audio pareidolia,

  • and it explains why you might hear a cryptic voice in radio static,

  • or someone whispering your name in the wind.

  • Basically, when your brain attempts to make sense from nonsense,

  • static and amplified background noise are shaped into vague words.

  • Add a little sprinkling of wishful thinking because you're trying to hear words from the other side,

  • and you end up with a full-blown ghost voicemail.

  • And the power of suggestion can even alter what message you hear.

  • As we explained when we talked about auditory illusions,

  • there are a lot of factors that can affect how your brain interprets ambiguous sounds.

  • Experiments from both white noise and human speech have demonstrated that

  • if subjects are given context beforehand,

  • their interpretation of a recording tends to match their preconceived expectations,

  • even if the provided context is deliberately incorrect.

  • So if we were to play you something we recorded in the Old Sawmill across town at 3 AM the other night,

  • your impression would be very different if we told you that it saidGET OUT

  • *static*

  • than if we told you the message wasEIGHT COWS”.

  • *static*

  • Still, in either case, the recording in question wasn't actually speech or words at all,

  • it was just ambient noise.

  • So now you may be saying,

  • Nice try Scishow, but you're not going to convince me

  • that ghosts are just when people get confused about motion off to the side or mis-hear static.”

  • And fair enough.

  • So let's crank up the science.

  • Another device no serious paranormal investigator would be caught dead without is an EMF detector.

  • EMF, of course, stands for electromagnetic field:

  • the area of radiation that surrounds flowing electrical currents.

  • These fields can be naturally occurring or can come from electronics,

  • and they range in frequency.

  • Now, paranormal investigators will tell you that EMF detectors track ghosts

  • because their incorporeal forms generate EMFs.

  • But some scientists think what's really going on is the opposite:

  • EMFs may actually cause the feeling of being haunted.

  • We mentioned a while back that some ghost stories can be explained by the phenomenon of infrasound.

  • Those are sound waves with frequencies below the normal human range of hearing.

  • And though you can't hear them,

  • they still make things in your body wiggle around a bit like other sound waves do,

  • leading to everything from the feeling of being watched to outright seeing apparitions.

  • And EMFs might be kind of similar.

  • But instead of vibrating our bodies, they mess with our neurons.

  • Laboratory studies have demonstrated that low-frequency EMFs can darken our mood

  • or cause other negative psychological effects when applied to regions of the brain.

  • And the effects can be much stronger, including visual hallucinations.

  • The catch is that not everyone may be affected the same way, if at all.

  • For example, the relatively minute EMF of an alarm clock

  • was enough to make one patient hallucinate nighttime visitors in her bedroom.

  • But, it turned out the magnetic pulses generated by the clock were similar

  • to ones that can induce seizures in some people.

  • And in this case, there was a specific interaction between the clock's EMFs

  • and the patient's existing brain injury.

  • Because these fields can have such strong psychological effects,

  • some scientists think the ubiquitous EMFs of the modern era are responsible for a lot of,

  • if not most ghostly experiences.

  • But, while the alarm clock was a slam dunk,

  • definitively tracking down EMF sources in every haunting isn't so straightforward.

  • EMFs can come from oodles of sources, including just about every electronic device out there,

  • so with all the WiFi and smartphones and such these days,

  • it's nearly impossible to accurately isolate and assess the effects of specific electromagnetic signals.

  • Still, if a paranormal investigator tries to tell you that an EMF spike means there's a ghost in the room with you

  • you can tell them your BS detector is also spiking.

  • Some of the creepiest supposed encounters with ghosts

  • are those that don't occur in some creepy, haunted place.

  • They happen right in your bedroom.

  • Midnight visitations by shadowy figures are a major feature of personal ghost encounters,

  • and probably the freakiest of all.

  • But your brain is probably to blame here, too,

  • and a weird phenomenon called sleep paralysis.

  • In short, your body is asleep but your brain isn't quite,

  • and you get left experiencing an honest-to-goodness waking nightmare.

  • Sleep paralysis tends to happen when the normal brain processes tied to sleep are accidentally disrupted,

  • often due to some sort of chronic mental stress.

  • Neither your body nor your brain are fully awake, so you're somewhat aware of your surroundings,

  • but still unable to move, and this is the key bit, still possibly dreaming.

  • Which is why people experiencing sleep paralysis often hallucinate.

  • Science isn't entirely sure why yousee” a ghostly form instead of other things,

  • but it may have to do with how sleep-related brain processes go haywire.

  • In the lab, if you tamper with a part of the brain called the temporoparietal junction,

  • you can give people out-of-body experiences,

  • because it's a key part of how we sense and recognize our own body.

  • It's normally not active when you're asleep, but it could be activated or partially activated during sleep paralysis.

  • And that might mess with it just enough for you to sense your body as someone else.

  • You might even be convinced that other person is somewhere else in the room.

  • Some psychologists have suggested that just the right neurons firing at just the wrong time

  • may cause us to use the built-in blueprints of our bodies to hallucinate another being.

  • And once that happens, mirror neurons could play a role in bringing that imagined other person to life.

  • These are neurons that fire in response to actions we see performed by others, and, importantly,

  • which fire in the same way when we perform these actions ourselves.

  • If, during sleep paralysis, these neurons are firing while other weird neurological effects are happening,

  • you could potentially misinterpret a self-made projection of another person,

  • which is doing stuff your mind is making up,

  • as an autonomous entity controlling its own actions.

  • In other words, your natural sleep cycle gets interrupted, your bleary brain makes you see a person,

  • and then it tricks you into thinking that person is moving around right before your eyes.

  • Meanwhile, all you can do is you look on, helplessly frozen in place.

  • It might be terrifying, but it's nothing more than a sophisticated bad dream.

  • None of this is to say that anyone's haunting experience is any less valid or panic inducing,

  • just that not every one of these experiences should lead us to conclude that the answer isghosts”.

  • Ultimately, there's plenty out there that we don't understand, and yes, that can be frightening.

  • But in many cases, our lack of understanding is only because we haven't found the solution yet,

  • not because things are too horrific or too unknowable to ever make sense to us.

  • The world, and your brain, has a lot of weird stuff it can throw at you,

  • but understanding it can make it less scary!

  • And science will always be there for you, to make the paranormal just... normal.

  • Thanks for watching this episode of SciShow!

  • If you liked learning about the weirdness of your brain,

  • you'll probably love our sister channel, SciShow Psych.

  • There, we dive into all sorts of questions about how human brains work

  • and why they do strange things like make you see beings that aren't really there.

  • Just head on over to YouTube.com/SciShowPsych to check it out!

  • [♪ OUTRO]

[♪ INTRO]

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あなたの脳内でバンプを行くもの:幽霊の4つの科学的な説明 (Things That Go Bump in Your Brain: 4 Scientific Explanations for Ghosts)

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    林宜悉 に公開 2021 年 01 月 14 日
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