Research Shows That Fish Can Do Basic Arithmetics
There is a common belief that fish have a memory that lasts three seconds. Hence, a forgetful person is told to have the memory of a fish. Perhaps, for this reason, the fish swimming from left to right and from right to left in the circular aquarium of your living room may seem oblivious to life. It does not concern them whether their aquarium has been moved so long as they have water in it, or whether the face of their feeder has suddenly changed so long as they are fed.
Like many other assumptions about animals, this seems to have been proven wrong. The research group led by Prof. Dr. Vera Schluessel from the Institute of Zoology at the University of Bonn has assessed the mathematical ability of fish in research including colors, addition, and subtraction. The research group has shown that cichlids and stingrays were capable of more than detecting small quantities without counting, and actually had the ability to calculate (1).
Deciding on the procedure was the difficult part; how could you ask a fish to carry out an addition?
Their method was crafted with inspiration from research made on bees. The group attributed meanings to colored geometric shapes. If the shapes were colored blue, it meant “add one”, if they were colored yellow, it meant “subtract one”. With these attributed meanings, the fish were shown a collection of shapes colored either blue or yellow, for example, three circles. This was the original stimulus. Then they were shown two new collections. The first one consisted of two circles, and the other consisted of four. If the circles were blue they had to swim towards the collection of four circles, if they were yellow, the fish had to swim to the collection of two circles. If they swam to the correct collection they were rewarded with food. Over time, they were conditioned to make a relation between blue and adding one, and yellow and subtracting one. On average, it took the cichlids 28 sessions to correctly solve the math problems and 68 sessions for the stingrays. In general, they performed well although addition was easier to learn.
This was a surprising finding for the researchers since the reason for the fish’s need for mathematical skills is unknown — it does not have an obvious benefit in evolution. A suggestion the researchers have come up with was that “Arithmetic abilities could be one of many cognitive byproducts that may be useful to enhance individual recognition (e.g. by using phenotypic characteristics) or help detect changing environmental or socials conditions,” and “As both species live in complex habitats (rocky lake and coral reef environments), a certain degree of behavioral flexibility is essential for survival,” (2). Thus, while possessing these mathematical skills might be advantageous in several situations, not possessing them does not put them in a disadvantaged position.
As the researchers have written in the journal of Scientific Reports, “Again, this raises the question of what abilities fish may be capable of if being asked the ‘right’ question.”