(ORDO NEWS) — Scientists have found that Zebra mbuna fish and stingrays are able to add and subtract numbers.
In the experiments, the fish had to swim through the chambers, where they were given a reward-delicacy only if they correctly counted in their minds.
In a study published in the journal Scientific Reports , scientists from the University of Bonn found that the Mbuna zebra ( Pseudotropheus zebra ) and rays ( Potamotrygon motoro ) are able to add and subtract one from the numbers one to five.
How was the experiment?
The researchers developed special cameras that separated the two screens. Images were shown on each screen: for example, five dots on one and three on the other screen.
The fish randomly chose a side and received (or did not receive) a reward. Over time, they learned to associate the visual stimuli on the screens with the desired outcome.
After that, the researchers complicated the task: at first, the fish were shown either yellow or blue figures.
The animals were given 5 seconds to remember the number and color of the figures; then the gates opened and the fish had to choose between two doors with screens: one with an additional figure and the other with one less figure.
Blue represents addition and yellow represents subtraction.
For example, if a fish was shown an image with three blue figures, then it had to add one to three and choose a gate with four figures in order to receive a reward.
Eight mbuna zebras and eight rays participated in the study. Of these, six mbuna zebras and three stingrays learned to count: they coped with the tasks 78 and 94% of the time, respectively.
Subtraction was more difficult for them: both types received correct answers in 69 and 89% of cases, respectively.
Now scientists plan to complicate the tasks. They also note that the results add to a growing body of evidence that the cognitive abilities of some fish need to be re-examined.
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