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Fish handle numbers on par with college students

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We can leave all the jokes aside but an interesting study has found some fish to score just as well as college students on some basic number tests. Using the highly social, freshwater mosquitofish the researchers conducted a lab test showing the fish could in fact count — differentiating between numerical quantities in a lab experiment.

It seems the mosquitofish are always looking for company and if one finds itself alone, its first priority is to find other mosquitofish. Using this behavior, lone fish were trained in the lab to associate a door bearing a certain number of geometric shapes with the path to rejoining a larger group. The fish were put in tanks and had to chose between one of two identical doors bearing different numbers of symbols. After time the fish were able to distinguish between the smaller and larger numbers, in essence counting.

“You just don’t expect interesting results like this when dealing with animals like fish,” said study leader Christian Agrillo of the University of Padova in Italy. “We thought this was really incredible.”

When the team changed the ratios between the numbers, the fish were effected as well with slight initial confusion — something the team also noted in the human volunteers in the experiment.

“It was kind of funny, most of them appeared to be surprised when we switched from small numbers to hundreds. They swam inside the tank for a while, looking at the new stimuli as if they were trying to understand what was going on,” Agrillo said. “However, after a short while they started to solve the task as well.”

As the researchers adjusted the numbers of shapes on the doors, the fish were less successful when the numbers were closer to each other. With a higher differential, such as four to eight shapes, in the ratio the fish fish would chose the right door more often. As the numbers of shapes got closer together the fish would struggle.

So how about the comparison to humans? The researchers took a group of 25 undergraduate students to try a test that had the same types of challenges, where the students would have to differentiate and find the larger number in two seconds. The research found humans were more accurate in the tests over the fish but showed the same degraded ability to judge number differences as ratios shifted higher.

The counting-fish study was published December 22 in the journal PLoS ONE.

[via National Geographic]


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