Not Good at Math? Blame Your Inner Fish

New research suggests that female mosquitofish can count, but only up to four with any precision. No word on how high male mosquitofish can count. The research design is quite clever:

When males bother females, the females try to flee to the biggest group of nearby females. When given the choice between two groups — one with three other fish and another with four — the females consistently choose the group with four. When the choice is six vs. seven, they act like they can’t tell the difference. (Although maybe they count that high and they just don’t care about six vs. seven.)

They do, however, distinguish between groups that are twice as big as other groups even when the numbers are big (e.g. eight vs. sixteen). According to the article, this puts the mosquitofish on par with young children, and apparently, any human who does not have access to language as a way of helping with the counting.

As an example, Christian Agrillo, an experimental psychologist at the University of Padua in Italy, claims that the indigenous people who speak Munduruku in the Amazon don’t have words for any number higher than five, and these folks don’t count much better than the fish.

One needs to be a little careful with the direction of causality here, however. Perhaps the fact that the Munduruku don’t bother with numbers higher than five is an indicator that math isn’t really their thing to start with. (Hat tip to the always-interesting folks at Spectre.)

The similarity between fish and humans caught my attention because I’ve been reading a delightful little book by my University of Chicago colleague (who I don’t think I have ever met), Neil Shubin, entitled Your Inner Fish.

Shubin, a paleontologist, makes a convincing case for us being very fish-like physically and anatomically:

The same bones that make up fish fins are in our hands. Early on, human embryos and shark embryos look a whole lot alike.

There are dozens of examples. Perhaps this should not be surprising given that we evolved from fish, but I had never really thought about the details before. The best thing about the book is that Shubin absolutely loves what he does with the sort of child-like innocence that often typifies the best scientists. His enthusiasm is infectious.