Cuttlefish Can Count to Five, New Study Shows

Some say language is the operating system for the human brain. While computation metaphors tend to diminish the reality of cognition, this one at least feels appropriate. It's difficult to imagine thought without language and vision without symbolism. What would quantities look like to a mind without numbers?

On that last count, we find answers in the study of innate number sense. It's what happens when the brain absorbs numeric information from the environment. It's not math, and it doesn't involve actual numerals, as these are human inventions. Instead, it's a primal aspect of sense cognition.


A prime example of this is logarithmic counting, or counting based on integral increases in physical quantity. A human infant without the faintest notion of numerals can still look at a bunch of six bananas and a bunch of two bananas and recognize the difference. This power, however, seems to dull as the ratio between quantities becomes smaller.

That's what makes the cuttlefish so interesting, based on findings from a recent Taiwan's National Tsing Hua University study published in the journal Nature. Researchers Tsang-I Yang and Chuan-Chin Chiao put a cuttlefish into a tank, along with a transparent two-chambered box. Each side of the box contained a different quantity of shrimp, forcing the cuttlefish to choose the better of the two. They changed the shrimp ratio each time and even played around with larger and dead shrimp to see how those conditions factored into the cuttlefish's decision-making.

The researchers tested 54 different pharaoh cuttlefish (Sepia pharaonis) and found that the creatures had no problem picking larger quantities of shrimp over smaller quantities. No surprise there, but their ability to choose the richer shrimp chamber pulled through even in cases of narrow ratios, such as 4 shrimp in one chamber and 5 in the other.

In fact, the researchers theorize that given the longer computation time in these incidents, the cuttlefish are not only thinking logarithmically, but are also actively counting the shrimp as they zip around in their respective boxes.

The creatures' performance, according to the researchers, ranks their number sense among primates and human infants. They can count to five and perhaps higher, even though they lack the language, numerals or symbolism to codify the information.

That is, unless cumulative levels of hunger appeasement constitute a language or number system. Perhaps you seafood lovers can test it out for us: The next time you dig into a plate of shrimp, see if you can count to five with the alien, unlanguaged, non-numeric mind of a cuttlefish.