The math-savvy animal club is growing. A team of German researchers has just shown that two species of fish are capable of adding and subtracting.
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We knew that certain birds, monkeys or insects knew how to count but this time we call on the board two species of freshwater fish: on the one hand rays from South America and on the other hand small blue zebra fish. German researchers from the University of Bonn have succeeded in giving them math lessons in the aquarium using a color code. When they showed them cards with blue geometric figures, one had to be added and when the drawings were yellow, one had to be removed.
The fish responded by swimming towards the correct answer. When they saw a card with three blue patterns, you had to count plus one and therefore go through a door with four blue shapes. Conversely, when faced with four yellow shapes, four minus one had to be calculated and the fish had to move towards the door with three yellow shapes. Knowing that behind the right door, there was a food reward. Result: more than half of the 16 fish tested were able to associate yellow with subtraction and blue with addition.
If it had just been a coincidence, there would have been 50% correct answers but there was between 80% and 94% success depending on the exercises. We note that the two species of fish are better at addition than at subtraction and that overall, rays are a little better than zebrafish in mental arithmetic. Fish like humans are therefore not all equal when it comes to numbers. These very serious works were published in the Scientific Reports magazine.
What good is it for a fish to have the maths bump? Researchers think it helps them survive. For example to recognize their congeners or predators, by counting the spots or stripes on their body. It is also important for moving around in a group, or measuring quantities of food. Despite their small brains, these fish therefore have the same mathematical background as pigeons, parrots, crows and salamanders. We are talking here about counting to four only.
Among invertebrates, only bees know how to count to five – they also master the notion of zero – which puts these bees at the level of a child in the first year of kindergarten.