Fish are usually seen as dunces in the animal kingdom because of their poor memory. But a new study led by scientists from the University of Bonn suggests that this view may be a little misguided.

They taught stingrays and zebra mbuna addition and subtraction and found that they can do maths much like humans. Their findings highlight that the numerical abilities of fish are on the same level as those of vertebrate and invertebrate species.

Fish are Smarter Than Previously Thought: Scientists Teach Stingrays, Zebra Mbuna Fish to Add and Subtract
(Photo : Pixabay/anncapictures)
Fish are Smarter Than Previously Thought: Scientists Teach Stingrays, Zebra Mbuna Fish to Add and Subtract

Math Lessons for Fish and Stingrays That Taught Them How to Add and Subtract

Professor Vera Schluessel from the University of Bonn in Germany and colleagues have been training fish in numerical tasks for a few years before the publication of their study.

According to IFL Science, one of the math lessons that the team gave the stingrays and zebra mbuna (a type of african cichlids) included putting them in a compartment separated by two screens in which researchers would present different things on each screen. For instance, they would present five dots on one screen and three on the other.

Then the fish will choose a side to swim through randomly and either receive a reward or get nothing. After a series of sessions, the fish gradually learned to associate visual stimuli with the desired outcome on the screens.

After learning the basics, the researchers then tested the knowledge of the stingrays and cichlids by projecting geometric shapes in specific colors that represented whether the answer involved subtraction or addition by a factor of one. Blue shapes signal addition so that the fish will look for a screen option showing four blue triangles.

Meanwhile, yellow shapes signal subtraction by a factor of one. When shown the three yellow shapes, the fish correctly chose the two triangles on the screen. They first learned it through trial and error and gradually learned to make sense of the numerical tasks presented to them as they were motivated by the food reward.

It only took 28 sessions for the zebra mbuna to learn the task. Meanwhile, it took stingrays 68 sessions to pick up the process. So, the fish learns faster than stingrays. However, stingrays scored higher when it comes to accuracy.

For the addition tasks, zebra mbuna scored 296 out of 381 (78%) while stingrays made fewer mistakes 169 out of 180 (94%). For the substraction tasks, zebra mbuna made 264 correct answers out of 381 (69%) while stingrays scored 161 out of 180 (89%), SciTech Daily reported. Both fish were slightly less reliable with subtraction.

The promising results are just the beginning of exploring the intelligence of fish and the team hopes to conduct another experiment that is a bit harder next time. They published the full findings of their study, titled "Cichlids and Stingrays Can Add and Subtract 'One' in the Number Space From One to Five," in the journal Scientific Reports.

ALSO READ: What's the Most Talkative Fish? Researchers Reveal These Species Appeared 155 Million Years Ago!

How Smart Are Stingrays?

A 2010 report from Phys.org about the bizarre water spouting behavior of stingrays showed how smart they are. Dr. Michael J. Kuba, the leader of the stingray project in the zoo, explains that the water spouting behavior may be due to the small food remnants that remained lodged in the duckweed in the aquarium.

More so, they appeared to have associated humans with food and started to spout water as soon as humans approached their aquarium. The stingrays were challenged to get food out of a pipe that researchers prepared, wherein each had two colors of the end: white to open, and the black end is closed. Soon, the stingrays were able to distinguish them and successfully received the food reward.

The previous study and the current study show the cognitive ability of stingrays in problem-solving, tool use, and doing maths. Most importantly, it proves that they are smarter than most people think.

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