Cuttlefish Pass ‘Marshmallow Test,’ Showing Impressive Self-Control

Cephalopods conquer task designed to test self-control in children.

Common cuttlefish (Sepia officinalis)
Common cuttlefish in the Atlantic Ocean. A. Martin UW Photography / Getty Images

Delayed gratification is hard enough for humans. But a new study finds that cuttlefish — members of the cephalopod family — have the patience to avoid something good now in order to plan for something even better to come along.

The study is a version of the famed “marshmallow test” designed by Stanford University researchers in the 1960s. A child is left alone in a room with a marshmallow. They’re told that if they don’t eat the treat, they’ll get a second marshmallow when the researcher returns in 10-15 minutes. If they give in and eat the snack, there’s no second marshmallow.

The kids who managed to exert self-control often were more likely to perform better on academic tasks.

Some animals also have managed to show self-restraint in tasks like this. Some primates will be patient in order to get a greater reward. Dogs and crows have also exhibited self-control in animal versions of the marshmallow test.

Now common cuttlefish (Sepia officinalis) also show the benefits of hanging tight.

Practicing Self-Control

For the experiment, researchers placed cuttlefish in a specially designed tank with two separate, clear chambers. In the tanks were a piece of king prawn and live grass shrimp, which was a much more appealing food.

Each chamber had a different symbol on the door, which the cuttlefish learned to associate with accessibility. A square meant it wouldn’t open. A circle meant it would open right away. And a door with a triangle could take anywhere from 10 to 130 seconds to open.

In a test, they were able to eat the king prawn immediately. But if they did, the shrimp was taken away. They could only eat the shrimp if they didn’t eat the prawn.

All six cuttlefish waited for the shrimp and ignored the prawn.

“Generally, the cuttlefish would sit and wait and look at both food items as if contemplating the decision to wait to take the immediate food option. On occasion, we noticed that our subjects would turn away from the immediate option as if to distract themselves from the temptation of the immediate reward,” lead author Alexandra Schnell from the University of Cambridge’s department of psychology, tells Treehugger.

“This is commonly observed in other animals such as apes, dogs, parrots, and jays. However, further research is needed to determine whether this turning away behaviour is indeed self-distraction or whether the cuttlefish just had their eye on the prize (their preferred food).” 

The cuttlefish with the most control waited as long as 130 seconds, which is an ability compared to big-brained animals like chimps, Schnell says.

In a second experiment, a gray square and a white square were placed randomly in the tank. The cuttlefish were rewarded with food when they approached a specific color. Then the reward was switched and they quickly learned to associate the other color with food.

The researchers found that the cuttlefish with better learning performance also showed better self-control. This link exists in humans and chimps, but this is the first time it has been demonstrated in a non-primate species, Schnell says.

The results were published in the journal Proceedings of the Royal Society B.

Recollecting Past Memories

Earlier research found that cuttlefish keep track of what they’ve eaten, where they've eaten it, and how long ago they ate. They use those memories to fine-tune where they go to forage.

“This type of memory, called episodic-like memory, was once thought to be unique to humans. It has since been discovered in rodents, brainy birds (crows and parrots), apes and cuttlefish,” Schnell says.

“Recollecting past memories is thought to have evolved so that humans and animals can plan for the future, the memories essentially act as a database to predict future events. Seeing as cuttlefish can remember past events, I wondered whether they could also plan for the future - a type of intelligence that is quite sophisticated.”

But before Schnell and her colleagues could determine whether cuttlefish could plan for the future, they had to first figure out whether the cephalopods could practice self-control.

“You see, self-control is an important pre-requisite for future planning because one must deny themselves in the present moment to obtain better outcomes in the future,” she explains.

The Benefits of Waiting

Now that researchers know that cuttlefish can practice self-control, the next question is understanding why.

The benefits to apes and brainy birds are obvious, Schnell says. Resisting temptation in the present in order to wait for better choices can lead to increased longevity and can strengthen social bonds.

In addition, apes, crow, and parrots might resist hunting or foraging in the moment in order to build tools so that they can optimize their hunting outcomes. But none of these benefits apply to cuttlefish that live short lives, aren’t social, and don’t use tools.

Instead, researchers speculate that cuttlefish evolved self-control to fine-tune their eating habits.

“Cuttlefish spend the majority of their time camouflaged, remaining motionless to avoid detection by predators. These long bouts of camouflage are broken when the animal needs to eat," Schnell says.

"Perhaps they evolved self-control to optimise their hunting excursions, as waiting for better quality or preferred food might expedite their hunting experiences and also limit their exposure to predators.”

View Article Sources
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