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April 4, 2008

Fish add up, but not past four

Posted: 12:47 PM ET

We all know one fish and one fish make two fish, but recent evidence suggests that fish may know that too. In fact, mosquitofish can count up to four, according to results from a team of researchers led by Angelo Bisazza of the University of Padua in Italy.

In each test, a lone female mosquitofish had two options for shoals to join, each containing between two and eight other fish. The results showed the lone fish would usually choose the shoal that was larger by just one fish, consistently picking the shoal of four fish over the one with three, and the shoal of three fish over the one with two.

But when one of the choices was larger than four fish, the fish could no longer discriminate. Monkeys and one-year-old children exhibit the same limit, Bisazza said.

Experiments examining what the fish would do when confronted with larger numbers found that, for shoals of more than four fish, they could still tell the difference between the quantities if there was at least a 2:1 ratio. That is, they would choose a shoal of eight fish over the one with four, but they could not discriminate between a shoal of 12 and a shoal of eight. These results are consistent with mathematical abilities observed in birds and mammals.

Similar performance has also been observed in people who speak languages that contain limited vocabularies for numbers, Bisazza said. For instance, speakers of the Amazonian language Munduruku only have words for numbers from one to five, and do not have names for numbers beyond that. Though they are able to solve nonverbal number tasks involving quantities up to 70, in exact arithmetic they do not do well with numbers larger than four or five, he said.

Besides fish, other non-human creatures that have shown at least some rudimentary mathematical abilities in studies include chimpanzees, macaques, dolphins, dogs, parrots and pigeons.

"Many researchers are now convinced that mammals and birds may share common mechanisms to count objects and compare quantities," Bisazza said.

–Elizabeth Landau, Associate Producer,

Filed under: Animals • Mathematics

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Fish can count - but only up to 4 « exploring our world   April 5th, 2008 3:22 pm ET

[...] Fish can count – but only up to 4 One, two, three, four... hmm, what comes next? I'd hope you know, but a 1-year-old child might struggle. Monkeys generally can't get past 4 either, and neither can fish – as scientists have now discovered. [...]

Three fish, four fish…then no more fish « Water Ouzel   April 5th, 2008 9:15 pm ET

[...] Tags: evolution, science, self study CNN's blog arena recently published this little report on the counting abilities of the fishies.  Evidently, just like monkeys and one-year old children, [...]

Derek McCrea   April 6th, 2008 12:24 pm ET

Wow, it is amazing that fish actually know that, science can really tell us some facts.

Derek McCrea

Mr. Spock   April 6th, 2008 3:03 pm ET

Was this fish-study earmarked?

California Boy   April 7th, 2008 4:10 am ET

the world population of fish, mainly the ocean fish, would prosper better if there were hydrogen powered ships like the hydrogen powered cars. Nobody worries about polluting the ocean only carbon emissions in the atmosphere

Patrick Anthony Drake   April 7th, 2008 10:38 am ET


Richard   April 7th, 2008 2:30 pm ET

Cool. I think it's interesting that while we have scientists working on curing AIDS, we also have scientists working out how far fish can count. Hey, there's nothing wrog with a bit of fun now and again I suppose. 😆


juniah   April 7th, 2008 2:56 pm ET

someone had to place last in the graduating class!

Fish Can Count Up to Four « The Intelligencer: Oddities & Curiosites   April 7th, 2008 7:12 pm ET

[...] [...]

danodelion   April 8th, 2008 2:28 pm ET

How do the researchers know that the fish are comparing numbers rather than geographical or spatial area of the group, i.e., that they aren't just entering the larger school for the sake of safety?

vita kelley   April 10th, 2008 2:55 pm ET

One more reason to be VEGAN.

gbls   April 11th, 2008 5:44 pm ET

@ danodelion

Regarding your first question: how do scientists know that they aren't comparing spatially relative sizing?

Scientists would claim that they must be, considering that they can tell a group of 8 is twice as large as a group of 4. They are using the fact that the fish are able to discriminate between a group of 3 or 4 as being able to tell the difference of a 33% gain in size. This would generally lead to a hypothesis that they are able to enumerate the set of fish in each grouping.

As for the choice based on safety: Who cares what the motive is?

Motive does not affect ability to distinguish numerical value. As a matter of fact, the very fact that you mention one group being larger than the other presupposes the fish are able to utilize some metric with which they can evaluate the size of the group of fish. You can't assume something you are trying to prove. It's bad math and bad science.

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How much of my tax money was spent on this crappy study??

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