Fish keep surprising us with their unexpected skills. We previously wrote a story on how goldfish can be trained to operate a vehicle and another about how some work together as superorganisms and basically use radar technology. On top of all this, would you have ever guessed that they can perform mathematical equations?
A team from the University of Bonn found that cichlids (a species of freshwater fish) and stingrays can carry out simple addition and subtraction from one to five. Studies have shown some fishes’ ability to count before—along with other animals such as bees and parrots—but what makes this project different is the impressive displays of their calculation skills.
“Many people think that they’re really stupid—fish in general,” says lead author Dr. Vera Schluessel in a press release. “They actually do have personalities … and they also can learn quite complex tasks.”
How are fish trained to calculate?
“We trained the animals to perform simple additions and subtractions,” explains Schluessel. “In doing so, they had to increase or decrease an initial value by one.”
Using a method already tried and tested on bees, the team used shapes and numbers to allow the animals to communicate their answers: blue shapes represented “add one”, and yellow represented “subtract one”. The animals were shown a picture with shapes such as squares, circles, and triangles of a particular color. Five seconds were given to memorize the image, and two solutions were given: a picture with one more shape and a picture with one less.
If the shapes in the first picture were yellow, the fish had to choose the solution with one less; if they were blue, the correct choice was the picture with one more. When the creatures calculated the answer correctly, they were rewarded with a tasty treat in the form of earthworms, mussels, or shrimps for stingrays and pellets for cichlids.
Performing well above chance
The fish performed well outside of the margin of chance, with stingrays completing addition calculations with an accuracy of over 96 percent and cichlids with over 82 percent. They both found subtraction a little more challenging, but this is no surprise since human toddlers do too.
“So, the animals had to recognize the number of objects depicted and at the same time infer the calculation rule from their color,” Schluessel says. “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 afterward. Overall, it’s a feat that requires complex thinking skills.”
This contributes to humans seeing fish as sentient creatures and making us reconsider how we treat them. Commercial fish farming practices can be extremely cruel, and there is little welfare regulation in place across the world that could help decrease these animals’ suffering. The authors believe research such as this will help chip away at human exploitation of sea life and treat fish with more respect.
Source study: Scientific Reports – Cichlids and stingrays can add and subtract ‘one’ in the number space from one to five
