A very patient cuttlefish
The cephalopod aces the marshmallow test
Cuttlefish are one of the sea’s most wondrous creatures and can change color and texture to evade capture. New research suggests the cephalopods also have amazing self-control. A group of Cambridge University scientists subjected cuttlefish to a version of the famous experiment known as the marshmallow test and published the results in a March 3 report. It’s the first time scientists have demonstrated self-control in an invertebrate.
Stanford psychologist Walter Mischel popularized the marshmallow test in the 1970s to analyze self-control and the ability to delay gratification. Researchers placed children before a table containing a treat and told them if they could wait 15 minutes without eating, they could have more. Later experiments used marshmallows, giving the experiment its name. Mischel used the test to connect childhood self-control to life outcomes, though later work called his conclusions into question by arguing he didn’t adequately control for factors like socioeconomic differences.
But what sort of self-control do cuttlefish have? In the experiment, Cambridge scientists designed a feeder with three doors marked by a circle, triangle, or square. The researchers trained the cuttlefish to get food by selecting one of the doors. Behind one door, scientists placed a small piece of shrimp. Behind another, researchers placed a full-sized live shrimp. The third door never opened. To test cuttlefish intelligence, scientists put the door hiding the full meal on a timer, making the animals wait for their prize.
Each cuttlefish preferred to wait up to 130 seconds for a shot at a full, live shrimp rather than choosing the quicker, smaller piece. The creature displayed self-control “comparable to what we see in large-brained vertebrates such as chimpanzees, crows and parrots,” the researchers wrote.
Other intelligent animals form advanced social bonds or use tools, but scientists aren’t sure why cuttlefish are so smart. The marine mollusks are opportunistic eaters, taking on shrimp, crabs, worms, and small fish when they have the opportunity. But the small cephalopods must be careful to avoid becoming a meal for dolphins, sharks, seals, or larger fish. Cuttlefish use color changing camouflage and shapeshifting to disappear.
Lead author Alexandra Schnell speculated that the animal uses its patience and intellect to wait for good meals on the sea floor. “They break camouflage when they forage, so they are exposed to every predator in the ocean that wants to eat them,” Schnell said. All the more important, she reasoned, to be patient.
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