Cuttlefish Pass the Marshmallow Test by Exerting Self-Control

Humans tend to underestimate the intelligence of other animals since their "smart" behavior doesn't include, say, kittens going to Mars. However, a new test conducted on common cuttlefish (Sepia Officinalis) has revealed one interesting aspect of its intelligence: self-control.

These results, published today in the journal Proceedings of the Royal Society B, present the first evidence of a connection between self-control and intelligence in a non-primate species.

Cuttlefish was tested with a new version of the Stanford marshmallow test. This test is usually conducted by placing a child in a room with a marshmallow. According to the rules, if they don't eat the marshmallow for 15 minutes, they'll win a second marshmallow, and be allowed to eat both.

In this version of the experiment, cuttlefish in tanks were given two food they commonly eat in separate Perspex chambers. One of the chambers had a piece of king prawn, available to eat immediately. The other had a live grass shrimp, which they preferred more, but they could only eat it if they waited and didn't eat the prawn. 

At first, the researchers started at 10 seconds, then increased the delays by 10 seconds each time. All six cuttlefish showed self-control and waited for the grass shrimp and ignored the king prawn. Those with the most self-control even waited a total of 130 seconds for the superior meal.

"It was quite astonishing that the cuttlefish could wait for over two minutes for a better snack. Why would a fast-growing animal with an average life-span of less than two years be a picky eater?" said Dr. Alexandra Schnell in the University of Cambridge’s Department of Psychology, first author of the paper.

This is incredibly interesting since this ability to wait 130 seconds to land a higher-quality prey is comparable to large-brained animals like chimpanzees.

Self-control vs. learning ability

The researchers then tested the learning ability of each cuttlefish by placing a dark grey market and a white marker in random positions in the tank. After they learned that one color was associated with a reward, the reward was switched to the other color.

Those who had shown more self-control in the first task were better at this test, too -- they were both quicker to learn the association and realize when the switch happened. "This link exists in humans and chimpanzees, but this is the first time it has been shown in a non-primate species," said Schnell.

While the research is a clear indicator of the cuttlefish's ability to self-control, the reason why is up to speculation. "Cuttlefish spend most of their time camouflaging, sitting, and waiting, punctuated by brief periods of foraging," Schnell said. "They break camouflage when they forage, so they are exposed to every predator in the ocean that wants to eat them. We speculate that delayed gratification may have evolved as a byproduct of this, so the cuttlefish can optimize foraging by waiting to choose better quality food."