APR 18, 2022 10:00 AM PDT

Some Fish Species Can Count

WRITTEN BY: Ryan Vingum

If someone asked you if fish could count, your response would probably be… probably not? Counting seems like an ability far beyond the cognitive functions of a fish, right?

Perhaps not.

While the notion that fish can tell the difference between small quantities has been established (for example, telling the difference between two or three of something), new research suggests that certain fish species actually have the ability to count and do basic calculations.

A study published in Scientific Reports recounts an experiment designed to understand the ability of fish to perform basic addition and subtraction calculations. Cichlids and stingrays, specifically. 

But asking either of these species is surely a challenging task, right? You can’t just ask a fish “What’s 1+1” or 4-1.” In order to test the calculative abilities of cichlids and stingrays, researchers devised an experiment that used colors to communicate certain mathematical functions the research team wanted fish to perform. Specifically, researchers showed the fish different groups of shaped objects in different colors. Blue objects represented “addition” and yellow objects represented “subtraction.” 

For example, researchers could show the fish four blue circle shapes, highlighting they wanted the fish to add. After showing this initial stimulus, researchers would show them another stimulus. The next stimulus would represent the addition the fish were to identify (e.g., they would show fish five circles and another option with three circles). If fish swam to the five circles (the correct option), they were rewarded. 

However, researchers wanted to test if fish were actually “learning” to add, rather than just internalizing what responses garnered a reward. To test this, researchers omitted a specific mathematical operation from the training session with the fish: 3+1 or 3-1 was never presented to the fish. The idea was to see if fish would recognize and apply their addition and subtraction knowledge, rather than just having internalized reward patterns.

Interestingly, fish frequently chose the correct stimulus for 3+1 and 3-1, despite having never seen it before. 

The results were quite interesting to researchers. They found the results especially interesting because these fish species don’t have a cerebral cortex, which is responsible for more complex cognitive activity. There were also questions raised about how the fish used these mathematical abilities: there was no known need to count eggs or find a sexual partern, so how did these fish use their numerical abilities?   

Sources: Science Daily; Scientific Reports

About the Author
Master's (MA/MS/Other)
Science writer and editor, with a focus on simplifying complex information about health, medicine, technology, and clinical drug development for a general audience.
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