You’ve probably heard of the Stanford Marshmallow Test. You know, the one where children are given a marshmallow but told if they wait 15 minutes to eat it, they’ll get two. It turns out that children aren’t the only ones who can pass the test. Cephalopods, also known as Cuttlefish, have also been added to that list. (1)
The Cephalopod Passes Cognitive Test For Human Children
The cephalopod, or cuttlefish, has passed its own version of the Stanford Marshmallow Experiment. This study shows that the ocean-dwelling fish have the ability to learn and adapt and delay gratification if they know that something better is coming. (1)
In February 2020, a group of researchers from Cambridge University discovered that cuttlefish put on a feeding schedule could not only learn the schedule, but they would eat less crab meat during the day knowing that a more desirable meal is provided later on. (1)
This proved that cephalopods have the ability to have complex cognitive thought processes by showing their capacity for future planning. (1)
Ph.D. student Pauline Billard says she and the team were impressed at how quickly the cuttlefish learned and adapted.
“It was surprising to see how quickly the cuttlefish adapted their eating behavior – in only a few days, they learned whether there was likely to be shrimp in the evening or not. This is a very complex behavior and is only possible because they have a sophisticated brain,” she remarked. (1)
How The Study Worked
Cephalopods are both selective and opportunistic foragers. When the researchers reliably provided them with a shrimp dinner each night, they ate less of the provided crab during the daytime. When the shrimp provisions were random, they ate more of the daytime crab. (1)
The fish were able to switch back and forth between the two eating patterns quite quickly. They made sure to eat enough food; however, they held out for it when they knew the good stuff was coming. (1)
“This flexible foraging strategy shows that cuttlefish can adapt quickly to changes in their environment using previous experience,” said study lead Professor Nicola Clayton of the University of Cambridge’s Department of Psychology. “This discovery could provide a valuable insight into the evolutionary origins of such complex cognitive ability.” (1)
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A Follow-Up Study
Though the first study provided valuable information, it was unclear as to whether the cephalopods’ decisions were based on the ability to use self-control or not. To test this, the researchers designed a second study on the fish. (2)
This time, the cuttlefish were put in a special tank with two see-through compartments that contained food. One was a simple piece of raw king prawn shrimp, the other a much more desirable live grass shrimp. (2)
Each compartment had doors that could open and close with symbols overtop. The fish were trained to know that a circle meant the door would open immediately, whereas a triangle meant there would be a delayed opening anywhere between 10 and 130 seconds. A square was used in the controlled edition and meant that the door would never open. (2)
In the test group (circle vs. triangle), if the cuttlefish went for the piece of prawn, the live shrimp was taken away. In the control group, the live shrimp was locked away behind the square symbol door. (2)
In the test group, every single cuttlefish waited for the live shrimp. In the control group, they didn’t bother because they knew they would never be rewarded for their patience. (2)
“Cuttlefish in the present study 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.” explained lead author Alexandra Schnell. (3)
The cuttlefish that learned the quickest were also the ones who exerted the most self-control. (3)
Why Do Cephalopods Do This?
Cuttlefish are not social, so they are not saving food to ensure that everyone in the group gets some. They don’t use tools to forage or eat, nor do they hide food for later as other animals do. So what makes cephalopods do this? (3)
The researchers believe this is likely because they spend most of their time in camouflage, waiting for prey to come by. To break camouflage to forage means to make themselves vulnerable to predators. If they know that better food is guaranteed if they wait, they will hold off until the tastier meal comes by. (3)
Next, the research team wants to study the fish to learn whether they can plan for the future.
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Sources
- “Cuttlefish eat less for lunch when they know there’ll be shrimp for dinner.” Eurekalert. February 4, 2020.
- “Cuttlefish exert self-control in a delay of gratification task.” Royal Society Publishing. Alexandra K. Schnell, et al. March 3, 2021.
- “Quick-learning cuttlefish pass ‘the marshmallow test’.” Eurekalert. March 2, 2021