Stingrays and zebra mbuna fish showing fewer than five shapes can add or subtract “one” from the total for a reward
March 31, 2022
Stingrays and zebra mbuna fish can perform simple addition and subtraction operations involving numbers between 1 and 5.
Multiple studies show that fish can distinguish higher and lower numbers. But it’s unclear whether they could perform mental tasks to add and subtract numbers from each other.
Vera Schlusser At the University of Bonn in Germany and her colleagues designed tests to determine whether stingrays (potato) and Zebra Buna (fake zebra) A value of “one” can be added or subtracted from a number between 1 and 5.
The team first trained six zebras and four stingrays to make choices after seeing an initial stimulus. Fish start with a section where they are shown an initial picture of two shapes for 5 seconds. After this time, they could swim through an open door to a test area, where there were also pictures of two shapes: one showing a single shape and the other showing three shapes.
If the two shapes in the initial picture are yellow, if the fish swim toward an image that shows only one shape (subtraction), they are rewarded in the test area. If two shapes in the initial image are blue, the fish is rewarded in the test area for swimming toward the image showing three shapes – an addition operation.
Once the fish were trained to associate yellow with subtraction and blue with addition, the team tested their counting ability. In the first test, animals were presented with initial images of three shapes, either yellow or blue. Then, in the test area, they could choose between two shapes or four. Zebra mbunas correctly selected the addition (quad-shaped option) 82% of the time when they saw the blue stimulus, and successfully selected the subtraction (dual-shaped option) 68% of the time after the yellow stimulus. At the same time, Stingray successfully added 96% of the time and correctly subtracted 90% of the time.
The team then explored whether the animals simply chose more or fewer shapes, or whether they actually learned to add or subtract a shape from the initial conditions. In this case, the choice is to add one or two blue shapes if the initial stimulus is blue, and to subtract one or two yellow shapes if the stimulus is yellow.
“They have to remember what they saw before and have to add or subtract exactly one,” Schluessel said.
Zebra mbunas correctly chose to add one instead of two 70% of the time, and to subtract exactly one 66% of the time. Stingrays successfully chose to add one instead of two 90% of the time, and to subtract exactly one 87% of the time.
In all tests, the team controlled for the total area of the shapes in each image, as some thought the fish might simply be dealing with the combined surface area of the objects, rather than really calculating it the way we understand it.
“It’s amazing to see what capabilities these types of animals actually have when we give them a chance. Many people are against putting cows or chickens in small cages, but very few people fish on the street,” Schluessel said. “This is just one of many studies showing that perception and cognition in fish really deserve more consideration.”
Journal references: Scientific Reports, DOI: 10.1038/s41598-022-07552-2
register to wild wildlifea free monthly newsletter celebrating the diversity and science of animals, plants, and other strange and wonderful inhabitants of the planet
More information on these topics: