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  • [♪ INTRO]

  • Stefan: Hey Brit, did anyone ever tell you that goldfish only have a 3 second memory?

  • Brit: I don't thinkwait what was the question again?

  • < I see what you did there.

  • Well it turns out that so-called fact is just plain wrong.

  • The whole idea that fish don't have long-term memories and aren't very smart in general

  • probably arose because their brains look very different from ours.

  • And they're often thought of as primitive because they were among the earliest vertebratesthey

  • split off from the rest of the gang several hundred million years ago.

  • But of course, since then, fish haven't just stood stillor tread water?

  • They've continued to evolve, and their mental abilities have evolved along with them.

  • I was hoping that, as a host of our sister channel SciShow Psych, you could help me explain

  • how fish are actually pretty smart.

  • < < I'd love to.

  • The main reason many scientists thought fish were less intelligent than mammals is that

  • they don't have a neocortex.

  • That's the outer part of the brain found in mammals which is particularly large and

  • wrinkly in humans, and in us, it's responsible for higher cognitive functions like problem

  • solving, abstract thinking and planning.

  • So, it was long assumed that fish just couldn't do many of those things.

  • But in the past few decades, researchers have come up with clever ways to test their intelligence,

  • and fish keep excelling at those tests.

  • Take koi, those giant goldfish-like species that people keep in ponds.

  • Many people who keep them say that they can recognize the person that feeds them and know

  • when and where they'll be fed.

  • This is called time-place learning.

  • And scientists have found those koi keepers are right.

  • When they fed laboratory fish at one end of their tank in the morning and the other end

  • in the evening, the fish picked up the pattern and would wait

  • in the right place for their meals.

  • Fish are also capable of Pavlovian learning, just like dogs and many other vertebrates.

  • That's when an animal learns to associate a stimuluslike foodwith a completely

  • unrelated cuelike a bell.

  • For example, rainbowfish were able to associate a light turning on with food after about 14 repetitions.

  • It takes rats about 40 repetitions before they learn a similar association.

  • And the memories fish form last a whole lot longer than 3 seconds.

  • Lab experiments have shown that rainbowfish can remember the location of a hole in a net

  • for a whole yearand given that they typically only live about 2 years in the wild, a year

  • is a pretty long time.

  • And not only do their memories lastsome fish are really quick learners.

  • In a 2012 study, researchers gave cleaner wrasses, capuchin monkeys, chimps and orangutans

  • the same learning test by placing equal amounts of food on two colored plates.

  • One plate color was always removed when they ate from the other one, so the animals had

  • to learn which color to eat from first.

  • The fish were actually the first to pick that upmost of the primates never got it.

  • And they were also quickest to figure things out when the researchers switched which color

  • plate stuck around, thereby demonstrating reversal learning—a cognitive feat usually

  • associated with brain size, and therefore high intelligence.

  • Fish can also remember complex location information by creating something called a cognitive map.

  • It's kind of like the map of your neighborhood you have in your head.

  • And for frillfin gobies that live in tide pools in the Caribbean, having a good mental

  • map is a matter of life and death.

  • When scared, these gobies will leap out of their home pool into a neighboring one.

  • So they have to know where those neighboring pools are, otherwise they'll end up on the

  • rocksand become a tasty sea gull snack.

  • In the 1950s, researchers showed that gobies removed from their home pools for up to 40

  • days were still able to remember the location of neighboring pools and jump into them when scared.

  • And that's just one examplestudies have found other species can remember the locations

  • of food, predators, hiding places, and potential mates.

  • When it comes to navigation, fish seem to be every bit as skilled as their land-dwelling kin.

  • But navigation doesn't necessarily mean intelligence, at least not in the way that humans define it.

  • One of the high bars we set for intelligence in other animals is the ability to use toolswhich

  • scientists roughly define as using an inanimate object to do something you can't do with

  • your body alone.

  • Andsurprise!—there are fish that use tools!

  • Several species of wrasse have been shown to use rocks to smash open sea urchins.

  • And some freshwater fish that make nestslike cichlids and catfishwill glue their eggs

  • to a leaf or rock so they can pick them up and relocate them easily if the nest is disturbed.

  • Now, there is even some evidence that fish can do mathsort of.

  • They're not solving algebra problems, but they may be able to count, or at least tell

  • less versus more.

  • In scientific terms, this is called numerical competency.

  • This makes sense for schooling fish, since there's greater safety in bigger numbers.

  • But even non-schooling fish seem to have this skill.

  • A recent study used cards printed with dot arrays where the number of dots could be manipulated.

  • The researchers then trained goldfish to select the card with the most dots or the fewest.

  • And they trained a lot - they did about 1200 practice sessions.

  • In the end, these goldfish could distinguish between 10 and 15 dots.

  • And they could choose the most or fewest dots with about 91% accuracy.

  • That's comparable to the performance of non-human primates with similar amounts of training!

  • Some fish are socially adept, too.

  • They can tell individuals apart, remember who's who, and learn from their peers.

  • And some fish use their social skills to work with other species.

  • Perhaps the most impressive case of cooperation is the joint hunting done by groupers and

  • eels in the Red Sea.

  • A grouper will wake its normally-nocturnal hunting buddy during the day by approaching

  • a moray eel's cave and shaking its head in a particular way.

  • Then, the duo will take to the reefthe grouper snacks on small fish that the moray

  • spooks out of the reef into open water while the moray nabs the fish that dart into crevices

  • in the reef to escape the grouper.

  • Groupers will sometimes invite wrasses or octopuses to hunt with them, too.

  • And they can tell their partners where a fish is hiding by doing a special headstand!

  • All of which suggests they've got pretty stellar social cognitionthe cognitive processes

  • related to understanding and interacting with others.

  • Though it's clear that fish can recognize other fish, what remains contested is the

  • idea that they might be able to recognize themselves.

  • In theory, if an animal can recognize itself in a mirror and thereby pass the quote-unquote

  • mirror test, it has to have an abstract sense of self—a pretty heady concept that scientists

  • used to think was exclusive to us and our relatives.

  • But when exposed to a mirror, captive manta rays displayed unusual behaviorsthey blew

  • bubbles and rolled and unrolled the fins on the sides of their heads.

  • They don't do this to other manta rays, so the researchers believe these behaviors

  • are basically the fish's way of checking "is this me?"

  • Most recently, cleaner wrasses were given mirrors, and they seemed to pass, tooif

  • you want to learn more about that, I joined Brit on a whole episode about what happened

  • and what it really means, which you can watch over on SciShow Psych.

  • Overall, it seems like fish are probably about as intelligent as other non-human vertebrates.

  • Like mammals or birds, they can do some pretty smart stuffespecially species with really

  • complex social lifestyles, like cleaner wrasses.

  • A lot of this was probably overlooked because we humans had preconceived notions about which

  • animals were smarter than others.

  • And a lot of the time, we still bias our tests towards our ideas of intelligencethough,

  • we're getting better about that.

  • Intelligence is subjective, and it turns out when we design better tests, we find that

  • all sorts of species have cognitive abilities we never expected.

  • The question becomes how fish actually perform these higher cognitive functions without a neocortex.

  • They do have forebrainsthe part of the brain our neocortex comes fromand that

  • seems to be where some or all of this cognition takes place.

  • But their forebrains are smaller and less complex than the forebrains of mammals.

  • So it's still not entirely clear how such a “primitive designis able to

  • pull everything off.

  • And figuring that out can tell scientists a lot about how brains workeven ours.

  • < Thanks for watching this episode of SciShow!

  • And thanks to Brit for helping me wrap my head around fish intelligence.

  • you should check out our episode on the mirror test over on SciShow Psych.

  • < Yeah! And if you want learn more about how brains work or see more of Brit, be sure to subscribe

  • to the channel while you're over there!

  • [♪ OUTRO]

[♪ INTRO]

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B1 US fish cognitive brit intelligence goldfish grouper

Fish Are Way Smarter Than You Think

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    joey joey posted on 2021/05/05
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