A new test of smart cephalopods has confirmed how important it is for us humans not to underestimate animal intelligence.
Cuttlefish have been put through a new version of the marshmallow test, and the results seem to show there’s more going on in their strange little brains than we knew.
Their ability to learn and adapt, the researchers said, could have evolved to give squid a head start in the cutthroat marine world they live in.
The marshmallow test, or the Stanford marshmallow experiment, is pretty straightforward. A child is placed in a room with a marshmallow. They are told that if they manage not to eat the marshmallow for 15 minutes, they will be given a second marshmallow and they can eat both.
This ability to delay gratification demonstrates cognitive abilities, such as future planning, and it was originally performed to study how human cognition develops; specifically, at what age is a person smart enough to delay gratification if it means a better outcome later on.
Because it is so simple, it can be adapted for animals. Obviously, you can’t tell an animal that they get a better reward for waiting, but you can teach them to understand that better food comes if they don’t eat the food in front of them right away.
Some primates can delay gratification along with dogs, albeit inconsistently. Corvids have also passed the marshmallow test.
Last year, squid also passed a version of the marshmallow test. Scientists have shown that common squid (Sepia officinalis) can refrain from eating a meal of crabmeat in the morning once they learn that dinner is something they like much better – shrimp.
However, as a team of researchers led by behavioral ecologist Alexandra Schnell of the University of Cambridge point out in a new paper, it is difficult in this case to determine whether this change in foraging behavior in response to the availability of prey was also determined by a skill to exercise self-control.
So they designed another test for six common squid. The squid were placed in a special tank with two closed chambers with transparent doors for the animals to see inside. In the rooms were snacks – a piece of raw king prawn less favored in one, and a much more attractive live grass prawn in the other.
The doors also had symbols that the squid had learned to recognize. A circle meant that the door opened immediately. A triangle meant that the door would open after a time interval between 10 and 130 seconds. And a square, used only in the check condition, meant that the door would remain closed indefinitely.
In the test condition, the shrimp was placed behind the open door, while the live shrimp was only accessible after a delay. If the squid went before the shrimp, the shrimp was immediately removed.
In the meantime, the shrimp in the control group remained inaccessible behind the door with the square symbol that did not open.
The researchers found that all of the squid in the test condition decided to wait for their favorite food (the live shrimp), but weren’t bothered to do so in the control group, where they couldn’t access it.
“Cuttlefish in the current study were all able to wait for the better reward and tolerate delays of up to 50-130 seconds, which is similar to what we see in large-brain vertebrates such as chimpanzees, crows and parrots,” said Schnell .
The other part of the experiment was to test how well the six squid learned. They were presented with two different visual cues, a gray square and a white square. As they approached one, the other was taken out of the tank; if they made the “right” choice, they would be rewarded with a snack.
Once they learned to associate one square with a reward, the researchers switched the cues so that the other square now became the reward choice. Interestingly, the squid that learned to adapt the fastest to this change were also the squid that could wait longer for the shrimp reward.
That seems like squids can exercise self-control, but what’s not clear is why. In species such as parrots, primates, and corvids, delayed gratification has been associated with factors such as use of tools (because it requires planning ahead), food caching (for obvious reasons), and social competence (because prosocial behavior – such as ensuring that everyone has food – benefits for social species).
Cuttlefish, as far as we know, don’t use tools or cache food, nor are they particularly social. The researchers think this ability to delay gratification may instead have something to do with the way squids forage for food.
“Cuttlefish spend most of their time camouflaging, sitting and waiting, punctuated by brief periods of foraging,” said Schnell.
“They break camouflage when foraging, so they are exposed to any predator in the ocean that wants to eat them. We speculate that delayed gratification may have arisen as a byproduct of this, so the squid can optimize foraging by waiting to eat them. choose a better quality food. “
It’s a fascinating example of how very different lifestyles in very different species can result in similar behaviors and cognitive abilities. Future research, the team noted, should try to determine whether squids are indeed capable of planning for the future.
The team’s research is published in Proceedings of the Royal Society B