Squid can pass the “marshmallow test” – the famous psychological test of self-control.
In this case, the cephalopods were willing to forgo meals when they knew that waiting meant they would be rewarded with tastier treats, according to a new study. This makes them the first invertebrates to show the ability to exercise self-control.
The common squid (Sepia officinalis) – relatives of squid and octopus – are rogue hunters and impressive camouflage learners, with the ability to disappear quickly in any environment. They are also terribly clever; studies have shown earlier that they have a good memory, can learn the value of different types of prey and that they use experience from the past to help them predict where they can get food.
But before this study, it was unclear whether these creatures could also delay satisfaction.
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“Self-control is suspected to be the cornerstone of intelligence, as it is an important prerequisite for complex decision-making and planning for the future,” said lead author Alex Schnell, a research fellow in the Department of Psychology at the University of Cambridge. . Not all animals share this trait, and it was previously thought that those who do, such as great apes, corvids and parrots, has a long and social life.
To see if a cephalopod should enter the ranks, Schnell and her team have adapted the famous “marshmallow test” so that it appeals to squid. In the 1960s, Walter Mischel led an experiment at Stanford University to test how much self-control children have when they get a predilection like a marshmallow (or other treats like cookies and crackling) and two options: eat the one marshmallow now or wait for 15 to 20 minutes and be rewarded with two marshmallows.
In the current study, Schnell’s team swapped marshmallows for seafood restaurants after determining which preferred individual 9-month-old squid fish (not yet fully adult). It seems that everyone prefers the most lively grass shrimp, followed by king shrimp, while the Asian crab enters the last of the three.
After that, they set up a two-camera device with transparent drawers. Behind one drawer they placed a meal (like live grass shrimp) and behind the other a meal that was less preferred (like Asian crab). The doors had symbols on them that indicated whether it would open with a delay (a triangle) or immediately (a circle), which the squid learned to recognize.
The drawer with the less popular meal always opened immediately for the squid, but the other drawer opened after a delay. In the control mode, the door with the preferred snack did not open at all (a square). When the squid approached one room, the researchers immediately removed the snack in the other room.
A bit of a mystery
The squid did indeed prefer to postpone gratification to record a tastier meal if they knew the door would open after a delay; they could slow down their snack between 50 and 130 seconds. During this time, they usually sat at the bottom of the tank and looked at the two rewards, Schnell emailed WordsSideKick.
Sometimes they would even deviate from the immediate (less preferred, but currently available) option “as if diverting their attention from the temptation of the immediate reward,” she said. The same distraction technique has been previously observed in humans, chimpanzees, gays, parrots and dogs, she said.
“Why squid have developed the capacity for self-control is a bit of a mystery,” Schnell said. “This finding is an extreme example of concomitant evolution, because squid have evolutionary history significantly different from the monkeys, corvettes, and parrots being studied more, and yet they have the same cognitive trait.” (Convergent evolution occurs when different species develop similar traits independently.)
“Squid can tolerate delays in obtaining higher quality food comparable to that of some large brain vertebrae,” the authors wrote in the study. These include great apes, parrots and corvettes. But the benefits of self-control for such social and long-lived animals “are obvious,” Schnell said.
If these animals now resist temptation, they may have better results in the future and lead a longer life. These animals can, for example, wait for others to eat to strengthen social ties or to hunt and to search for food, to give themselves time to manufacture tools to optimize hunting and feeding in the future, she said.
The benefits for squid are less obvious. “Squid is not of long life, not social and does not manufacture or build tools,” Schnell said.
The researchers suspect that the squid developed self-control as a by-product of an unrelated trait: camouflage. To prevent predators from being detected, squid should spend long periods of their day in hiding and take only short breaks to feed. “Perhaps self-control has developed to optimize their feeding behaviors and reduce their exposure to predators,” she added.
The researchers also tested whether the degree of self-control in squid was linked to higher intelligence, or in this case, the squid’s ability to learn. To do this, they trained the squid to associate the reward with different stimuli; squid that exercised more self-control (waited longer to get food), according to the findings, had a better ability to learn.
To link self-control to intelligence, researchers need to study how the squid performs in other cognitive tests such as spatial memory and permanent object, which means an object continues to exist regardless of whether you can see it, Schnell said.
The findings were published in the journal on Tuesday (March 2). Proceedings of the Royal Society B.
Originally published on Live Science.