Do Fish Dream?
Articles, Blog

Do Fish Dream?

February 21, 2020


[♩INTRO] It’s easy to look at a sleeping dog, legs
twitching as she snoozes, and imagine she’s dreaming of chasing rabbits. And it’s only natural for us humans to wonder
if other animals dream. But dogs’ brains are relatively similar
to ours. What about something way more different from
us? Say, a fish? We don’t yet know exactly why our brains
race through fantastical or scary scenarios at night, but
there are plenty of hypotheses. Dreams may be ways for our brains to process
emotions or memories, or to prepare for new scenarios. Human sleep occurs in a series of cycles. We cycle through a series of phases over the
course of the night, which can take anywhere from 70 to 120 minutes. Most dreams occur during a phase called rapid
eye movement, or REM. As you might imagine, this type of sleep is
characterized by rapid movements of our eyes. It’s possible these eye movements are connected
to our dreams themselves. Researchers have suggested that each flick
of the eye may correlate with a new image being encountered in a dream. But do other animals experience sleep the
way we do? Well, we can’t exactly ask them, but we
sure are curious. And this fascination has led us to study sleep
in fish as far back as 1913. That study set out behavioral criteria for
fish sleep. In zebrafish, that means things like immobility,
a preferred sleeping location, and a reduced respiratory rate. But it wasn’t until a 2019 study that anyone
defined what was happening inside the brains of fish while they sleep. And it took so long because it’s hard to
do! One way to look inside human brains, including
during sleep, is using an instrument called an electroencephalogram,
or EEG. This typically measures activity in a region
of the brain called the neocortex. Fish don’t have a neocortex. However, zebrafish do have something similar, called the dorsal pallium, which the researchers
targeted in this study. They took advantage of the fact that the young
zebrafish are see-through. You can see straight into their brains! They inserted a gene into the fish that caused
their neurons to glow when active. Specifically, it gives off light in response
to calcium. Since calcium levels change as neurons send
their signals, this allowed the researchers to watch brain
activity while the fish slept. Their results showed that like humans, fish
cycle through sleep patterns. The researchers saw two main sleep states: slow bursting sleep and propagating wave sleep. And propagating wave sleep showed a number
of similarities to our own REM phase, though the fish’s
eyes stayed still. The researchers suggested these similar patterns
of sleep activity could have evolved before fish and humans
split, more than 450 million years ago. So, this doesn’t prove that fish can dream, but it suggests that they do go through something similar to our own dream-filled
REM sleep. So, that means fish dreams are a possibility! Thanks to our patron Olan Kenny for asking
this question. Our patrons submit and vote on questions that eventually get made into episodes like
this one! So, if you want to be a part of that process, or just want to help SciShow keep making free
educational videos for everyone you can check out patreon.com/scishow. [♩OUTRO]

100 Comments

  • Reply Thom McMahon February 19, 2020 at 12:27 am

    Better question was my first reading of the title: Do fish… SCREAM?!?

  • Reply Bruno Perlstein February 19, 2020 at 12:28 am

    Of course fish dream a dream about Hillary Clinton being hung by the neck until dead

  • Reply PDF February 19, 2020 at 12:40 am

    Do fish dream of electric eels?

  • Reply Dennis February 19, 2020 at 12:41 am

    They have wet dreams.

  • Reply ApexPredator_ February 19, 2020 at 12:48 am

    His hair looks like Mao Zedong's. I'm having Communist China vibes just by looking at him lol

    His stylist should re-style his hair next time.

  • Reply Avallac'h February 19, 2020 at 12:56 am

    I would never think about it in my life if it wasn't by this video. Thanks.

  • Reply Tina King February 19, 2020 at 1:01 am

    Amazing
    Thank you

  • Reply Xenomrph February 19, 2020 at 1:16 am

    I didn’t even know fish slept

  • Reply SSSpencer413 February 19, 2020 at 1:29 am

    Me: Maybe I’ll get more sleep tonight

    Also me at 3AM: Do fish dream?

  • Reply Theorica February 19, 2020 at 1:32 am

    Yes, yes, yes. Dreaming fish and all that. The real burning question we're all dying to know is do androids dream of electric sheep?

  • Reply Dark Bubbly Sugar Slime Drink® February 19, 2020 at 1:42 am

    fish dream about salt

  • Reply Kyler Chin February 19, 2020 at 1:52 am

    Noice

  • Reply Moonbeam February 19, 2020 at 1:53 am

    Do fish dream of soggy sheep?

  • Reply Milo February 19, 2020 at 1:55 am

    NOOOO….fish have souls…..

  • Reply Eddie February 19, 2020 at 1:57 am

    It's reasonable to assume that any creature that sleeps and also has functional memory can 'dream.' This opens the questions: 'what is sleep,' 'what are dreams' and 'what is functional memory'?

  • Reply Vasectomy Fail February 19, 2020 at 2:10 am

    dogs brains are similar to ours? is that why they look so stressed out when they're trapped in cars, as if they're thinking "hmm, why didn't my best friend take me with them?"

    i would hate to be leashed or neutered or have a microchip tracking implant or… oh yeah we're talking about fish

  • Reply E2qNX8btraQ3zRD6J7fc February 19, 2020 at 2:16 am

    Now I gotta see things light up in a fish brain while it sleeps. Did they use a camera or a photomultiplier tube to measure the 'light'?

  • Reply Wayne Searle February 19, 2020 at 2:21 am

    What about complex invertebrates like cephalopods?

  • Reply Rebekah February 19, 2020 at 2:43 am

    Sometimes when I close my eyes to sleep, I notice my eyes wandering around even though my they are closed. It's very distracting

  • Reply Lyndsay Brown February 19, 2020 at 2:51 am

    This research seems pretty fishy, but it's still got me hooked.

  • Reply Devon 831 February 19, 2020 at 2:54 am

    This sounds fishy

  • Reply Ivy February 19, 2020 at 2:57 am

    I wonder fish have nightmares where they end up on a chopping block or on some ones plate?🤔😂

  • Reply Alexander Ekrot February 19, 2020 at 3:00 am

    2:00 Isn't it sodium and pottasium levels that change? Might be both but just wondering.

  • Reply Greylintill February 19, 2020 at 3:07 am

    If they do dream, Do fish dream of electric eels?

  • Reply Paul van Aspert February 19, 2020 at 3:15 am

    Here's a 'DEEP' and profound question… Do fish ever get thirsty? Science… ya gotta love it! I know I do.

  • Reply Snakeseye Gaming February 19, 2020 at 3:27 am

    Aves

  • Reply Soul Platypus February 19, 2020 at 3:31 am

    the real question should be "Do fish dream of aquatic sheep?"

  • Reply Jeff Miller February 19, 2020 at 3:48 am

    Had a couple of friends who worked in a zebra fish lab. Always sounded like cool things were going on.

  • Reply Thomas Phillips February 19, 2020 at 4:01 am

    Don't gata tell me I had a dream visit with my fish and two others like it. But the other two were looking like spirit fish.

  • Reply Argha Deb February 19, 2020 at 4:13 am

    oh lord…lol

  • Reply Hugo Martinez February 19, 2020 at 4:16 am

    This is the exact questions we should be asking….

  • Reply Billy Yum Yum Two-by-Two February 19, 2020 at 4:21 am

    anyone here a dramatical murder fan wondering if jellyfish dream when they're asleep

  • Reply tinka patosi February 19, 2020 at 5:01 am

    They must have wet dreams 😁

  • Reply 20 points February 19, 2020 at 5:51 am

    Next question:
    Do plants sleep/rest regularly excluding any seasonal dormancy?

  • Reply ᪶ ᪶ February 19, 2020 at 6:00 am

    fish rem

    fish rem

  • Reply Adel Abdelazim February 19, 2020 at 6:24 am

    ممكن تضيفوا ترجمة عربي

  • Reply Adel Abdelazim February 19, 2020 at 6:26 am

    Can you add an Arabic translation for the videos?

  • Reply steven w February 19, 2020 at 6:37 am

    Fish dreams must be fascinating…

  • Reply FriedEgg February 19, 2020 at 6:38 am

    ..of electric eels?

  • Reply Jeremy C Barnhart February 19, 2020 at 6:45 am

    Interesting up until all credibility lost at 2:21

  • Reply Jolak Zmtag February 19, 2020 at 6:47 am

    BRUH fish get eaten every dam day. Id be having nightmares 24/8 😭

  • Reply Jacob Dial February 19, 2020 at 6:59 am

    im just a small town fish with dreams of making it in the big ctiy

  • Reply UseFreeSpeech February 19, 2020 at 7:07 am

    who cares?
    even if you care, does that video nothing for your curiosity. A Maybe are you kidding me?

  • Reply FvckYoutube'sCensorship UseAdblock February 19, 2020 at 7:12 am

    0:24 I guess that explains why I don't dream much anymore. These days I don't feel much of anything emotionally (just the way I like it) and memories I still have I'd rather forget if I could. No need to prepare for new scenarios either, every day has been pretty much the same as the one before for the past 14 years, no reason to think tomorrow will be any different.

  • Reply . February 19, 2020 at 7:24 am

    Do fish have wet dreams?.

  • Reply Michael Gibb February 19, 2020 at 7:26 am

    Do fish dream of aquatic sleep?

  • Reply Zes February 19, 2020 at 7:34 am

    wrg

  • Reply denshi.moe February 19, 2020 at 7:43 am

    Fish dream of aquatic sheep.

  • Reply Eric Serra February 19, 2020 at 7:45 am

    Where can I get these fish with glowing brains now? 😂

  • Reply Yasmin Raveh February 19, 2020 at 7:47 am

    I thought the title said "Do fish scream?" And was horrified to know the answer.

  • Reply Olly February 19, 2020 at 7:52 am

    Do animals have wet dreams?

  • Reply Jesko Parra February 19, 2020 at 8:01 am

    💡@ p_your:

    Clearly it means my spicy Darthsaber dreams….are just hoarseraddish.

    Also, I love oats as much as you may enjoy my Lightsaber: in a ricey-salmon-bowl covered in—

    Soy…does the sauce stick?

    …🙅…

    = Dude, I'm fracking hungdry.🗿

  • Reply Lili Marlene February 19, 2020 at 8:02 am

    This vid exemplifies the beauty of pure research…..research about a topic someone is just interested in. It isn’t done to find a cure for schizophrenia or cancer. It’s research just because someone said, “I wonder….”

  • Reply Brant Heilman February 19, 2020 at 8:37 am

    Do fish dream of aquatic sheep?

  • Reply di nf February 19, 2020 at 8:44 am

    of course, everything with sufficiently complex nervous system 'dreams', that line mostly correlates with vertebrates but also includes few other things eg. cephalopods

  • Reply Acedia DeKay February 19, 2020 at 8:57 am

    But do fish dream of electric eels ?

  • Reply Michel.rs February 19, 2020 at 9:00 am

    do fish dream of electric sheep?

  • Reply Christopher Noel February 19, 2020 at 9:01 am

    As a bird owner, I can attest that birds can have nightmares, which is why I keep them confined to their cage at night as much as I love letting them free range. Even with a nightlight, they'll crash into things in the middle of the night, so I keep them confined for their own safety. So, I would imagine that fish could have nightmares also. What our pets see in their dreams… I don't know, but I would imagine the experience is similar to humans.

  • Reply Jo.N Lam February 19, 2020 at 9:20 am

    😂😂😂

  • Reply Aranvar February 19, 2020 at 10:00 am

    Otherwise it would ruin the plot of the last Zelda game remake…

  • Reply Eli Ryan February 19, 2020 at 10:04 am

    I don't need sleep, I need answers

  • Reply John Thorpe February 19, 2020 at 10:17 am

    Perhaps a better question would be why are we so bloody arrogant that we assume that other animals don't experience what we do?

  • Reply Daruny Beoulve February 19, 2020 at 10:19 am

    So my fish dreams of me feeding it.
    Wholesome.

  • Reply donlars1 February 19, 2020 at 10:34 am

    Quote of the day "Fishdreams are a possibility!"

  • Reply Sanguine Sophrosyne February 19, 2020 at 10:37 am

    Do mechachondrichthyes dream of robot sheepfish?

  • Reply Ratstail91 February 19, 2020 at 11:08 am

    Answering the real questions.

  • Reply Praise The Masculine Flames February 19, 2020 at 11:31 am

    Do fish dream of aquatic sheep?

  • Reply Tim Sullivan February 19, 2020 at 12:14 pm

    Fish can even have a bad dream ( called a Night-Mer)

  • Reply pelle hyltoft February 19, 2020 at 12:24 pm

    Hurray for fishes do dream.
    I hope that our beloved akvarium fishes dream about…
    🙂 beautiful coral reefs and true fish love. (-:

  • Reply Hayen Da great February 19, 2020 at 12:48 pm

    If we can’t see air can fish see water

  • Reply akaMyThought February 19, 2020 at 12:50 pm

    Want to know a trick that I know that works. If your having a nightmare cross your eyes and you will cross your eyes for real and will wake up. Fyi for anyone that's having a night terror.

  • Reply chi-wei shen February 19, 2020 at 1:00 pm

    0:16 "But dog's brains are relatively similar to ours. What about something way more different from us?"

    Initially, only a sleeping woman can be seen.

  • Reply Anthony Martin February 19, 2020 at 1:01 pm

    I know dogs do have dreams, our dog used to talk in its sleep. little quiet woofs, and move his legs sometimes like hes trying to walk or run.

  • Reply Raymond Stemmer February 19, 2020 at 3:39 pm

    Fish go to school ! I knew a fish with a doctors degree !

  • Reply Dan Giles February 19, 2020 at 3:59 pm

    Yes, but do androids dream electric sheep?

  • Reply Mandu Rugas February 19, 2020 at 4:20 pm

    the fisherman's hook 2

  • Reply María Martínez February 19, 2020 at 4:30 pm

    How to answer a poetic question.

  • Reply hotdrippyglass February 19, 2020 at 5:12 pm

    +

  • Reply TacticusPrime February 19, 2020 at 5:19 pm

    Do fish dream of watery sheep?

  • Reply Max Roth February 19, 2020 at 5:34 pm

    When I eat pineapple, why does it itch?

  • Reply the whooshed February 19, 2020 at 5:39 pm

    OK how do we look inside fish brains?
    ……
    …….
    Make their brains glow
    THATS IT WE MAKE THEIR BRAINS GLOW

  • Reply I make comments cuz this is my commenting channel February 19, 2020 at 5:57 pm

    anyone else annoyed by “suh-NARR-reo”?

  • Reply Krzysztof Czarnecki February 19, 2020 at 6:43 pm

    Too bad you didn't put any video of those fish brain blinkenlights, that would be really interesting to see (totally not suggesting making a fish with RGB lighting with each color indicating a different neurotransmitter)
    Edit: there's a light-up fish brain video: https://www.youtube.com/watch?v=YLVdRPVj-XM

  • Reply marla rose February 19, 2020 at 7:04 pm

    Mabe my fish dream about me

  • Reply Chris Oliva February 19, 2020 at 7:18 pm

    Before explaining if fish dream, I would like a little elaboration on how on earth someone came up with the idea of looking into it.

  • Reply Rhys Kooy February 19, 2020 at 8:30 pm

    Bruh

  • Reply Existenceisillusion February 19, 2020 at 8:45 pm

    Do electric sheep dream of fish? That's what I really want to know

  • Reply Andres Evan Zavaleta February 19, 2020 at 8:57 pm

    Do fish dream of underwater sheep?

  • Reply DeathbyPixels February 19, 2020 at 9:27 pm

    Currently staring at Bagel, my betta fish, and questioning life.

  • Reply Iris Wijma February 19, 2020 at 9:28 pm

    The rest of the world: Coronavirus, Australian bushfires, yada yada yada

    SciShow: DO FISH DREAM??

  • Reply James Uthmann February 19, 2020 at 9:40 pm

    Oh no! Does this mean SciShow is now … "Sleeping with the Fishes"?

  • Reply John Stewart February 19, 2020 at 9:41 pm

    How big was the grant to $tudy dreaming in fish?

  • Reply Saphron February 19, 2020 at 9:47 pm

    …of aquatic sheep?

  • Reply Junior Mynos February 20, 2020 at 1:54 am

    Do all animals sleep?

  • Reply Angel Emmanuel Perez Muniz February 20, 2020 at 2:37 am

    Ask the wind fish. Link had to wake him up to exit from his dreams.

  • Reply PocketBoop February 20, 2020 at 5:49 am

    Do androids dream of electric sheep?

  • Reply ٰ ٰ February 20, 2020 at 10:57 am

    Octopus 🐙
    Dreaming
    Check the YouTube

  • Reply Nancy Votto February 20, 2020 at 1:31 pm

    It's not hard to believe everything goes through some type of sleep, even plants, and dreams are ways of those with brains to reboot and recharge.. Good thing God didn't make their pain heard to us, or we probably would have a harder time eating the poor things, as well as the other seafood around and plants.

  • Reply MrFresh3991 February 20, 2020 at 2:41 pm

    Do fish dream of sea sheeps?

  • Reply Holy Wasser February 20, 2020 at 6:49 pm

    Why haven’t we evolved to not have wisdom teeth yet?

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