fun facts

myth debunk: memo​r​y of a goldfish memory

You know this one: There is a popular belief that goldfish only have a three-second memory span.

We think that every circle of their fishbowl stroll is like seeing the world for the very first time.

So, to make my further myth debunking points, I’ll list just a few entry facts about the goldfish.

Eyesight is a highly developed sense of goldfish. In fact, they have vision superior then we do in some respects (they have night vision and they can see ultraviolet light).

Goldfish have a sixth sense. Tiny dots down each side of a goldfish, called the lateral line, represents an organ that actually gives a goldfish the ability to feel pressure changes in the water like vibration and currents. Goldfish can smell. Believe it or not, they actually have a better sense of smell than humans. In the winter goldfish kept outside go into hibernation.

And no, the memory span of goldfish is not 3 seconds.

It more than 3 months, actually.

We just “look” like “that” — Fish

There is something strange, deeply stereotyped about our attitude to fish in general. Or turkeys or sheep for that matter.

They are sorta dumb looking and they are smelly — a random human would say.

It is estimated there are a staggering 250,000 species of fish in our oceans, yet despite their diverse looks and behavior, many of us perceive them universally stupid.

People underestimate how smart fish are because we assume fish are primitive creatures. The reality is that most of the fish on the planet today evolved around the same time as humans.

In Finding Nemo, a Pixar movie from 2003, Dory the forgetful blue tang (Paracanthurus hepatus) tells Nemo: “I suffer from short-term memory loss… I forget things almost instantly.”

However, the widely-held biased belief that fish have three-second memories has been blown out of the water by animal behavior experts and scientists multiple times. Let’s go back to 1994.

Myth debunk time

The humble goldfish can remember things for three months, and can even tell the time in a rudimentary way. For a 1994 study, researchers trained goldfish to push a lever that worked for one hour a day in exchange for a reward. The fish learned to take advantage of this window of opportunity, demonstrating that they could keep track of time, learn and remember.

This will come as no surprise to owners of pet goldfish that beg for food at the water’s surface. Study author Phil Gee of Plymouth University in the UK says fish’s ability to anticipate food gives them “a competitive edge and an evolutionary advantage”.

Also, many fish can recall details for a very long time. For instance, the crimson-spotted rainbowfish (Melanotaenia duboulayi) can remember escape routes to evade danger for 11 months, according to a study published in 2001.

Most aspects of their cognitive abilities are just as good as most terrestrial animals, and in many cases even exceed them.

Guppies (Poecilia reticulata) can solve a maze consisting of six consecutive T-junctions. The popular pets not only learned to complete the puzzle but over a five-day training period they got faster and made fewer errors, according to a study published in February 2017.

The fish’s performance was surprising and could be compared to that of rats. Rodents are expected to be successful in similar tasks because they have evolved to live in burrow systems similar to that of a maze. But conversely, fish usually live in very different environments and therefore were not expected to rapidly learn the maze.

Guppies may have evolved their navigational abilities because, in the wild, they live in streams that are strewn with obstacles.

Fish, like mammals, have an excellent sense of space

Fish draw on incoming sensory information such as hydrostatic pressure to work out their position in three-dimensional space (according to a 2016 study). Fish can encode space in 3D, whereas land-dwelling animals like us have trouble with the vertical dimension. Unlike rats, fish can accurately judge vertical distance.

We can say that fish’s ability to track depth makes them “superior to humans” in this respect.

What are “Place cells”?

These cells, which have been found in rats, are neurons that fire when the animal occupies a specific location within its environment. Different place cells fire in different locations, so they are thought to be the seat of a neural map of space in mammals. So, if the animal, rat, or fish, recognize an environment, its place cells should fire in the same location as when they’ve already been in that environment.

The apparent fish “place cells” are in an area of their brain that is equivalent to the human hippocampus. The fish might use them to create a memory of the space around them.

As well as navigating, fish can use tools – a skill once thought to belong exclusively to humans.

Several of the brightly-colored marine fish called wrasses crush sea urchins against rocks to access the meat inside. Meanwhile, South American cichlids and hoplo catfish (Hoplosternum thoracatum) glue their eggs to leaves and small rocks, which they use as portable nurseries if their nests are under threat.

Perhaps the most impressive tool-using fish is the archerfish (Toxotes chatareus), which uses water as a tool or weapon, much as we might throw a ball. The fish squirts a jet from its mouth like a water pistol to hit insects above the water’s surface. It even takes light refraction into account.
After taking a shot and hitting its target, the archerfish calculates where its dinner will land and sets off at top speed to grab it ahead of its rivals. It can do this in as little as 40 milliseconds.

Archerfish just like goldfish can also discriminate between human faces, a task previously only accomplished by primates.

They can pick out a familiar face from a sea of 44 new faces, according to a 2016 study.

Researchers trained the fish to identify a familiar face by shooting it with a jet of water and discovered that they could make the distinction up to 89% of the time.

The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces.
Gee says there is a chance pet goldfish may be able to recognize their owners’ faces, although there is no evidence so far – and wild goldfish live in murky waters, which may mean they do not rely on vision as much as archerfish.

However, much like birds, fish can distinguish between quantities.
In a 2013 study, researchers found that newborn guppies can choose the larger of two groups of dots. Judging quantities is important for fish because they often avoid predators by joining large shoals. Several studies have shown that fish prefer to join the larger of two shoals when placed in an unknown environment.

As well as “counting”, fish can work together – even with members of other species.

Coralgroupers (Plectropomus pessuliferus) and coral trout (Plectropomus leopardus) both sometimes team up with snake-like giant moray eels (Gymnothorax javanicus) to flush out prey that is hiding in small crevices.
The trout and grouper both shake their heads to invite a moray to come hunting.

In a 2014 study, biologists showed that coral trout quickly learn to choose the most effective eel hunters. They used a set-up in which food was out of reach. The trout quickly worked out when they needed a collaborator to help them get the food, and they were three times more likely to choose an effective moray teammate over an ineffective one.

The experiment “strengthens the case that a relatively small brain, compared to warm-blooded species, does not stop at least some fish species from possessing cognitive abilities that compare to or even surpass those of apes,” says study author Alexander Vail of the University of Cambridge.
A goldfish aimlessly circling its bowl may not be as smart as this. But archerfish and other species are helping to challenge our perceptions of fish intelligence. Schuster says this should put our own cognitive abilities into context because clearly, impressive brainpower evolved long before humans.

However, it remains to be seen whether our scientifically proven appreciation of fish intelligence will ever be enough to put us all off picturing them as dumbasses. Or we are just dumb to prove animals’ intelligence in general. Oh, well.


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