School of fish head to class to learn basic math in new study

Ready to get schooled? A class of fish did, and it turns out they can do basic math.

Researchers at the University of Bonn in Germany reported in a study published on March 31 in the journal Scientific Reports that cichlids and stingrays were able to perform basic math functions with the numbers one to five.

In order to communicate with the fish, researchers showed the fish a certain number of geometric shapes in different colours. In the learning phase of the study, the researchers used these colours to teach the fish that the colour blue meant that they should add one, and the colour yellow meant that they should subtract one.

For example, the fish would be shown four blue squares. Then, after they had time to take in the four squares, they would be shown two new pictures – the correct answer depicting five blue squares, and one depicting an incorrect answer. When the fish swam to the correct answer, they received food to reward them for associating the colour blue with adding one. The exercise was repeated with the colour yellow, which signalled to the fish to subtract one.

But researchers also had to test whether this knowledge could be internalized and applied to other equations.

"To check this, we deliberately omitted some calculations during training," Dr. Vera Schluessel, the lead author on the study, said in a press release on April 1. "Namely, three plus one, and three minus one. After the learning phase, the animals got to see these two tasks for the first time. But even in those tests, they significantly often chose the correct answer."

The fish were also shown equations in which the objects of the same shape or size. For example, the number four could be represented by one small and one large circle plus a square and a triangle in one equation, but in another calculation could be represented by three triangles of different sizes and one square. Again, the fish were often able to select the correct answer.

"So the animals had to recognize the number of objects depicted and at the same time infer the calculation rule from their color," Schluessel said. "They had to keep both in working memory when the original picture was exchanged for the two result pictures. And they had to decide on the correct result afterwards. Overall, it's a feat that requires complex thinking skills."

While similar studies have been done before in other animals, including bees, researchers said they were surprised by the results because neither cichlids nor stingrays have a cerebral cortex, or the part of the brain that is responsible for similar cognitive tasks in mammals.

Other species also typically have reasons for developing simple mathematical skills, such as keeping track of eggs or babies, but researchers said that the reason these two fish species may use basic math in the wild is not yet known.