Cuttlefish Aced the Marshmallow Test Designed for Human Kids

Michael Walsh
·3 min read

You’ve probably heard about the famous Stanford “Marshmallow Test” before. It’s a simple experiment designed to see how much self-control children have. First you put a marshmallow in front of them. Then tell them if they can wait X minutes to eat it, they’ll get a second one. Turns out, it doesn’t tell us a whole lot about anyone’s future prospects or their ability to delay gratification. But it might reveal just how smart cephalopods are. Last year, cuttlefish passed a similar cognitive test. They’re smart enough to know to pass on the lunch menu when the dinner entrées are much better.

A team of researchers have published a paper (which we first heard about at ScienceAlert) at The Royal Society documenting their experiments with cephalopod self-control. They tested whether or not a single type of cuttlefish can delay gratification, much like the “Marshmallow Test” tests human children. They found the fish would pass on an early meal of crab once they learned their preferred meal of shrimp would be provided later in the day.

A yellow cuttlefish swimming in water with a small amount of green plants behind him on the left.
A yellow cuttlefish swimming in water with a small amount of green plants behind him on the left.

The New York Times

But the scientists couldn’t be sure if that was willful self-control or simply a reflection of the cuttlefish adapting to the general availability of their prey. To answer that, the team devised another, more conclusive test involving six types of common cuttlefish.

They placed the cephalopods inside a tank with two clear sub-compartments that held different foods. In one, the scientist put a piece of raw king prawn on ice. The other held the cuttlefishes’ much preferred snack, a live shrimp. Each compartment door also had a sign on it. Scientists trained the fish to recognize what each symbol meant.

A circle indicated the door would open immediately; a triangle meant it would not open for at least ten seconds up to two minutes and ten seconds; finally, a square meant it would stay closed indefinitely. All three symbols rotated in throughout, testing equally. Testing went on multiple times a day.

If the fish went for the prawn, the shrimp was immediately removed. Once they had eliminated any possible variables, researchers found the cuttlefish could in fact delay their own gratification. The team’s leader, Alexandra Schnell of the University of Cambridge, told EurekAlert all the fish “were all able to wait for the better reward and tolerated delays for up to 50-130 seconds, which is comparable to what we see in large-brained vertebrates such as chimpanzees, crows and parrots.”

The team thinks this skill might be related to a cuttlefish’s ability to camouflage itself. It tries to limit its exposure to predators. Having the patience to wait for better food would ensure safety while maximizing its enjoyment of its food.

The “Marshmallow Test” doesn’t tell us which kids will be more patient or successful teenagers. But it does tell us that animal kingdom is full of creatures with for our own instant gratification, it’s not clear our species can even pass the “Marshmallow Test” when it really counts.

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