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.
How can we really know that fish can’t count past 4? The method the scientists used was actually quite ingenious. They gave a lone female mosquitofish the option of joining two different shoals of fish, and found that it always preferred being in the larger shoal (more fish means increased safety from predators).
So, for example, it would always join a shoal with four fish in rather than one with three or two. And if there was a shoal with three fish in and a shoal with two, it would always go to the shoal with three of its fishy friends. But as soon as the shoals began getting bigger than four, the mosquitofish couldn’t figure out which shoal was best, and it just picked randomly.
By repeating this test several times, the scientists established with quite a large degree of certainty that mosquitofish can count, but only up to 4. (By the way, mosquitofish get their name from their habit of eating larval and developing mosquitos.)
They also discovered that when the fish was given the option of two shoals with a 2:1 ratio of fish in them, the mosquitofish would always join the larger one. So fish can do multiplication too? I doubt it – surely it’s just common sense once the differences between shoals become so great. But you never know what might happen now we’re in the age of genetic engineering…
Isn’t it great to know that while we have some scientists working on curing AIDS and saving our environment, others prefer to find out how good fish are at counting. What was the point of this experiment? I’m not entirely sure, but then again there’s nothing wrong with a bit of fun. And now you can pretend you’re a genius next time your kids watch Finding Nemo.