New Delhi: A species of cichlid fish and stingrays can perform mathematical operations, according to a new study. Cichlid fish species, Zebra mbuna and rays can perform addition and subtraction.
The results of the study were recently published in the journal Scientific reports.
According to the authors, the results show that the numerical capacities of fish are comparable to those of other species of vertebrates and invertebrates.
Fish recognize yellow and blue colors as symbols of mathematical operations
The mbuna zebra and stingrays can add and subtract one of the numbers one through five, according to the study. Professor Vera Schluessel, from the University of Bonn, Germany, who led the study, tested whether eight mbuna zebras (Pseudotropheus zebra) and eight freshwater stingrays (Potamotrygon motoro) could be trained to recognize color blue as a symbol for addition by a factor of one and the color yellow as a symbol for subtraction by a factor of one.
Depending on the study, blue or yellow cards were shown to the fish. Next, they were shown two doors containing cards with different numbers of shapes. One of the cards represented the correct answer.
How do fish perform mathematical operations?
For example, if a fish was shown a card with three blue shapes, it would add one to three and swim through a door containing the card with four shapes, according to the study. Also, if a fish was shown a card with three yellow shapes, it would subtract one from three and swim through a door containing the card with two shapes.
Fish that passed through the correct gate were rewarded.
How good were the fish at their tasks?
Six individuals of the mbuna zebra species and three of the stingrays learned to consistently associate blue with addition and yellow with subtraction, according to the study. It took an average of 28 sessions for mbuna zebras and an average of 68 sessions for stingrays to learn addition and subtraction.
Fish generally perform well in these tasks, but find it easier to learn addition than subtraction.
According to the study, individual fish performance varied more between Zebra mbuna and stingrays.
When the marine animals were given the addition task, the mbuna zebra selected the correct answer in 296 out of 381 tests, representing 78% of the tests. Meanwhile, the rays selected the correct answer in 169 out of 180 tests, which represents 94% of the tests.
Zebra mbuna was correct on 264 of 381 subtraction-related tests. This accounted for 69% of the tests. Stingrays selected the correct answer in 161 of 180 subtraction-based tests, which represents 89% of the tests.
Are numerical abilities important for fishing?
The authors believe that numerical abilities may not be very important for either species. The results, however, suggest that numerical abilities could help both species recognize individual fish by appearance. For example, the species can recognize individual fish by counting the stripes or spots on the fish’s body.
The authors noted in the study that the findings add to a growing body of evidence indicating that the cognitive abilities and sensitivity of fish need to be re-examined.