Guppies as good at counting as undergraduates

Fish can distinguish between two groups in the same way as humans.
19 February 2012


GuppiesA new study reveals that undergraduates and fish have a lot in common - at least when it comes to counting.

The old wives tale that fish have a seven second memory has been well and truly blown out of the water, with findings emerging that fish in fact have all sorts of elaborate behaviour; they can recognise, copy and deceive each other, and it turns out they can count.

Christian Agrillo of the University of Padova in Italy led a team of researchers who put the counting skills of guppies and human students to the test by asking them to pick the larger of two groups of things.

The undergraduates were shown a cluster of between 1 and 24 dots on a screen. One group of dots were flashed up for 150 ms followed by a second group for the same length of time but of a different number. The students were asked, without counting out loud, to choose which of the two groups had more dots.

The fish were tested by being offered a choice of who to hang out with - it's already known that guppies are quite sociable creatures and if they have the choice they prefer to join a larger shoal. The experimental fish were put in a glass tank resembling a miniature soccer pitch, with two shoals visible in each goal at opposite ends. The research team then watched them for 15 minutes to see which shoal they spent more time close to.

It turned out that both fish and college students performed almost identically in their tasks. They were both better at correctly picking the larger group of dots or fish when the ratio between the numbers was high e.g. they found it easier to distinguish between 24 and 4, than 24 and 20.

This only mattered up to the number four - below that, the ratio between the two numbers made no difference on their ability to pick out the larger group. Discriminating 3 from 4 was as easy as discriminating 1 from 4.

The fact that humans can do this should come as no great surprise - other primates have shown similar abilities. But the finding that guppies do it too is certainly intriguing, especially if you consider that primate brains tend to be around a thousand times bigger than their fishy counterparts. Being able to distinguish different sized shoals could clearly have an advantage for fish, but the study raises various questions about how these counting skills originated and whether it's independently evolved several times.

But as the authors suggest in their paper published in the journal PLoS One, these findings might hint that no matter how bad you think you might be at maths, our modern ability to do sums and count could have evolutionary origins way back among the ancestors us primates share with fish.


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