Aquatic animals are amazing! According to a recent study, cuttlefish have passed a new version of the marshmallow test, a cognitive test originally designed for human children.
The Stanford marshmallow experiment tests children’s grasp of delayed gratification. A child is left alone in a room with a marshmallow and told that if they do not eat the treat, they will get a second marshmallow and be allowed to enjoy both. By passing this test, children demonstrate cognitive abilities like planning.
Scientists have adapted the test for animals by teaching them that better food will come if they do not eat the food that is immediately available. In a 2020 study, cuttlefish—a type of cephalopod, a group that includes octopuses and squids—passed this test, refraining from eating crab in the morning once they figured out that by doing so they would receive something even better for dinner.
Intrigued by the results but recognizing shortcomings in the study’s design, members of the research team developed a new experiment. Led by behavioral ecologist Alexandra Schnell of the University of Cambridge, the team aimed to test whether the animals were actually exhibiting self-control.
The researchers placed cuttlefish in a tank that had two chambers separated by transparent doors so the animals could see the food inside. Each door had a symbol that the cuttlefish had been trained to recognize. The door with a circle would open immediately and give access to a less favorable treat, while the door with a triangle would open later and give access to a more enticing treat. If the cuttlefish took the first treat, the other one would be removed. But if they waited for the second door to open, they would be rewarded with the tastier food. Schnell said:
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.
The cuttlefish were also able to learn visual clues, realizing that squares of different colors represented different snacks and outcomes.
Studies like this only scratch the surface of the complexity of aquatic animals. Thankfully, more and more people are learning about these incredible beings. Recently, the popular Netflix documentary My Octopus Teacher helped viewers fall in love with an octopus off the South African coast. In the film, diver and filmmaker Craig Foster documented his amazing friendship with an octopus over the course of a year.
Despite these advances, aquatic animals still rarely get the respect they deserve. In fact, hundreds of billions are victims of the global fishing industry every year, either targeted as food or killed unintentionally as “bycatch.” And because we’re emptying the oceans of fish, populations of animals who depend on them for survival, such as cephalopods, pay the price.
Fortunately, it’s never been easier to withdraw our support from the cruel fishing industry and choose compassionate plant-based foods. For delicious recipes and easy meal ideas, get our FREE Vegetarian Starter Guide today.