A cuttlefish swims in an aquarium at the Scientific Center of Kuwait in 2016. Cuttlefish showed impressive self-control in an adaptation of the classic "marshmallow test." Yasser Al-Zayyat/AFP via Getty Images
By being able to wait for better food, cuttlefish — the squishy sea creatures similar to octopuses and squids — showed self-control that's linked to the higher intelligence of primates.
It was part of an experiment by Alex Schnell from the University of Cambridge and colleagues.
"What surprised me the most was that the level of self-control shown by our cuttlefish was quite advanced," she tells Lulu Garcia-Navarro on Weekend Edition.
The experiment was essentially a take on the classic "marshmallow" experiment from the 1960s. In that experiment, young children were presented with one marshmallow and told that if they can resist eating it, unsupervised, for several minutes, they will get two marshmallows. But if they eat it that's all they get.
The conventional wisdom has been that children who are able to delay gratification do better on tests and are more successful later in life. (There are of course many caveats when talking about the human experiments.)
To adapt the experiment for cuttlefish, the researchers first figured out the cuttlefish's favorite food: live grass shrimp; and their second-favorite food: a piece of king prawn. Instead of choosing one or two marshmallows, the cuttlefish had to choose either their favorite food or second-favorite food.
"Each of the food items were placed in clear chambers within their tank," Schnell says. "One chamber would open immediately, whereas the other chamber would only open after a delay."
It "essentially tested whether they could resist the temptation of their second preference food item and wait for their preferred food item."
The cuttlefish learned to wait.
"Animals like rats, chickens and pigeons, they find it difficult to resist temptation and have relatively lower levels of self-control, only waiting for several seconds," Schnell says. "Whereas animals such as chimpanzees, crows and parrots, they show more advanced self-control and they can wait up to several minutes. And the cuttlefish in our study waited up to between 50 to 130 seconds."
Animals that are able to exert self-control in this way have advantages. For example, animals can hide food to eat later, but they have to resist the urge to eat now.
The researchers say the experiment is the first evidence so far of this type of cognitive ability in an invertebrate.
In cuttlefish, Schnell thinks the delayed gratification relates to their lifestyle. They are masters of camouflage; they are able to blend into their environment and can stay perfectly still for long periods of time to avoid predators.
Then they forage for food in brief outings. "Individuals who wait for better-quality prey could forage more efficiently at the same time as limiting their exposure to predators," Schnell writes.
But to take things a step further, the researchers did a second experiment. They put colored markers into the tank and taught the cuttlefish to associate a certain color marker with food, by dropping food when the cuttlefish went to the marker. Then they swapped the colors.
The second experiment was to test the animals' "learning performance." The cuttlefish that were quicker to learn to associate and reassociate the markers with food were considered better learners.
They found the cuttlefish that were able to delay gratification the most also happened to be the ones that were better at learning. It's the "first demonstration of a link between self-control and learning performance outside of the primate lineage," Schnell writes.
Finding these similarities between cuttlefish and primates "is an important piece of the evolutionary puzzle," she adds.
Hence, the squishy cuttlefish is leading scientists a step closer to understanding more about the origins of intelligence.
Rosemary Misdary and Martha Ann Overland produced and edited the audio interview.
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