Fish Can “Count”, And This Discovery Could Help Humans Too

Zebrafish understand quantities like other animals. That may hint at a way to understand dyscalculia.


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

a zebrafish going mlep
You may not like it, but this is what peak performance looks like. Image credit: Kuznetsov Petr/

If idioms like “memory of a goldfish” or “drinks like a fish” are to be believed, then fish are nothing but a bunch of forgetful drunks, who are apparently extremely easy to shoot (in a barrel) but shouldn’t be allowed near criminal investigations (at least, if they’re herrings).

They’re not known for their wits, is the point. But a new analysis, published in the journal Frontiers in Neuroanatomy and based on a review of more than 200 studies, has found we may be doing the little fellas dirty: some fish are “on par with other animals in possessing a sense of quantity,” paper co-author Professor Giorgio Vallortigara said in a statement.


In other words: fish can do math.

Okay, okay, before any ichthyologists out there start writing angry letters, we should clarify – this is nowhere near the kind of math that humans are capable of. It’s the most basic form of numeracy possible: looking at two reefs and seeing which has more hiding places, for example, or figuring out whether more of your friends are swimming towards or away from the approaching shark. 

But just because it’s not the math we know and love, that doesn’t mean the result doesn’t impact us too. Far from it. 

“There are species, most notably the zebrafish, that are ideal models for studying the molecular and genetic bases of the sense of quantity,” Vallortigara explained. “This could have important implications for neurodevelopmental diseases affecting number cognition, such as developmental dyscalculia, which impairs math skills in up to 6 percent of children.”


This isn’t the first time animals have been found to “count” in this rough way – far from it, in fact: the ability has been recorded in everything from bees to bears, chickens and chimps, and of course the big daddy of animal math, crows. It’s “a big ongoing question” as to how and why all these different branches of the animal kingdom know how to “count” like this, Vallortigara explained – “the mechanisms for quantity cognition in the different parts of the animal kingdom [may have] evolved from a common ancestor or separately as a result of convergent evolution under similar selective pressures.”

The really cool thing, though, is that the fish are processing numerosity in a similar way to those “smarter” animals: “experiments are described in this review that show that pure numerousness is indeed used by fish,” said Vallortigara.

Zebrafish are no strangers to the neurology lab – not only are they surprisingly genetically similar to humans, they also have neat qualities like the ability to have a squillion see-through babies, making them a favorite model animal for biomedical researchers. They’ve been dosed with LSD, got drunk, and (unsurprisingly, given all those drugs and alcohol) got in fights for scientists’ amusement; we even managed to turn their thoughts into a screensaver at one point. 

That means we’re pretty good at understanding zebrafish brains – and we can use that understanding to study things like dyscalculia, the study explains. 


“Neural networks are highly conserved across vertebrates, and zebrafish have a relatively simple neural system and high homology with the human genome,” the authors write.

“A gene expression screening of nine genes …is associated with human developmental dyscalculia,” they explain. “[M]ost of them are largely distributed in the zebrafish dorsal pallium."

"With the establishment of robust assays of numerical abilities in zebrafish, we are well placed to test the causal roles of candidate genes and their mode of action.”


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