Two species of fish have the ability to do math

A recent study by a team led by Dr Vera Schluessel from the Institute of Zoology at the University of Bonn, is published in the journal Nature. Scientific Reports shows that striped fish and rays can perform simple calculations.

Suppose there are some coins on the table in front of you. If the amount is small, you can immediately know exactly how many coins there are. You don’t even have to count them – one glance is enough. The zebrafish (Pseudotropheus zebra cichlid) and freshwater stingray (Potamotrygon motoro) are amazingly similar to humans in this: they can accurately detect small numbers and perhaps do not need to count. Through training, they can correctly distinguish numbers under 5.

Dr. Schluessel explains: To train the fish, the researchers showed them cards one at a time. On the card are blue boxes for addition, and yellow for subtraction with different amounts.

For example, the fish is shown the blue card number 3, adding the number 1, the fish must find the box number 4. If a fish swims through the correct gate, they will be rewarded.

Researcher Vera Schluessel and colleagues performed on eight striped fish and eight rays.

The researchers found that six of the zebrafish and three of the stingrays were able to associate blue with addition and yellow with subtraction.

On average, the zebrafish learned the calculations after 28 lessons and the stingray after 68 lessons. For them, addition is easier than subtraction.

In the addition test, zebrafish chose 296 correct answers out of 381, accounting for 78% of the test, and stingrays chose 169 correct answers out of 180, accounting for 94%.

In the subtraction test, the zebrafish got 264 correct answers out of 381 questions, and the stingray got 161 correct out of 180.

“The animals had to recognize the number of objects and at the same time deduce the calculation rules from their colors. Overall, it was a feat that required complex thinking skills.” Vera Schluessel, Institute of Zoology at the University of Bonn.

This is a surprising discovery because fish do not have a cerebral cortex – the part responsible for complex cognitive tasks in mammals.

Previously, researchers had found that mathematical abilities also appear in gorillas, monkeys, dolphins, elephants, birds, salamanders, even bees and spiders.