The cuttlefish can pass the marshmallow test

Some species show a remarkable ability to delay gratification, including great apes, corvids, and parrots, while other species do not (such as rodents, chickens, and pigeons.) Add cuttlefish to the first one. category.

Scientists administered an adapted version of Stanford’s marshmallow cuttlefish test and found that cephalopods could delay gratification, that is, waiting a bit for preferred prey rather than settling for less prey. desirable. The cuttlefish also performed better in a subsequent learning test, according to a new article published in the journal Proceedings of the Royal Society B. This is the first time that such a link between self-control and intelligence has been found in a non-mammalian species.

As previously reported, the landmark Behavioral Study by the late Walter Mischel involved 600 children between the ages of four and six, all from the Bing Nursery School at Stanford University. He would give each child a marshmallow and give them the option to eat it immediately if they wanted. But if they could wait 15 minutes, they would receive a second marshmallow as a reward. Then Mischel left the room, and a hidden video camera would record what happened next.

Some kids just ate the marshmallow right away. Others have found a practical distraction: covering their eyes, kicking the desk, or pricking the marshmallow with their fingers. Some smelled it, licked it, or took tiny nibbles on the edges. About a third of the children lasted long enough to earn a second marshmallow. Several years later, Mischel noticed a strong correlation between the success of some of these children later in life (better grades, greater self-confidence) and their ability to delay gratification in kindergarten. Mischel’s follow-up study confirmed the correlation.

Mischel himself cautioned against overinterpreting the results, pointing out that kids who just can’t stand up for that second marshmallow aren’t necessarily doomed a life of failure. A more nuanced picture was offered by a 2018 study that replicated the marshmallow test with preschoolers. He found the same correlation between later accomplishments and the ability to resist temptation in preschool, but this correlation was much less significant after researchers took into account aspects such as family background, environment. family, etc. And a 2020 German study adapted the classic experimental setup using Oreos and vanilla cookies with German and Kenyan schoolchildren. This study found that children are more likely to delay gratification when they are dependent on each other.

Other selected species have also shown the ability to delay satisfaction through “forward-looking foraging”. Monkeys and corvids, for example, respond to a variable and unpredictable food supply by not immediately eating certain food items to prepare for any future shortages. Cambridge University biologist Alexandra Schnell, lead author of this latest study, wanted to explore whether cuttlefish (Sepia officinalis, a relative of octopus and squid), could also demonstrate self-control, during a fellowship at the Marine Biological Laboratory in Woods Hole, Massachusetts. Previous studies had shown that cuttlefish could optimize foraging behavior and could remember details of what, where and when past forages, adjusting their strategy in response to changing prey conditions. But was this future-oriented search for food a proof of self-control?

To find out, Schnell and colleagues first performed tests to determine the preferred prey of the six 9-month-old cuttlefish used in their experiments: live grass shrimp, live Asian shore crab, and pieces of raw king prawns. Cuttlefish have proven to be quite picky eaters, showing the least preference for Asian shore crab; some cuttlefish would not eat the crab at all. Between the two remaining prey types, cuttlefish showed a marked preference for live grass shrimp over raw king shrimp.

For the experimental setup, the team 3D printed a two-chamber device, consisting of two black plastic drawers, each with a transparent sliding door so the cuttlefish could see the contents. Each room has been given its own uniquely shaped detachable symbol. The team placed the device in an aquarium and then used PVC barriers at the other end of the tank to keep the cuttlefish equidistant from the two chambers.

Then the cuttlefish went through a double phase of training. In the first, the cephalopods were placed in the aquarium and then presented with a single chamber marked with one of the visual symbols, to train subjects to associate this space with a particular degree of accessibility to the prey. For example, a symbol was associated with immediate accessibility to the prey (instant gratification); another was associated with delayed release, followed by access to prey (delayed gratification); and a third was associated with inaccessibility to the prey (no satisfaction). In the third option, the cuttlefish would encounter a clear barrier protecting them from prey after opening the sliding door after a short delay.

The second phase of training involved a one-choice selection. There were two unmarked chambers (no associated symbol) baited with the same type of prey. When the cuttlefish made a “choice” by approaching one of the chambers, the prey in the other chamber was immediately removed. Test subjects also went through a pre-test phase to teach them that the duration of the prey accessibility delays would increase consecutively. In this pretest, the length of the delay ranged from two to 20 seconds, and each cuttlefish had to “choose” between an immediate and a deferred option.

For the actual experiment, the cuttlefish had to choose between two different prey: it could choose to eat the raw king prawn immediately or delay the gratification of the preferred live grass shrimp. (A control group of cuttlefish had to choose between immediate access to prey and no access.) Subjects could see both options for the duration of the trial and could forgo waiting at any time and eat the king shrimp if they had had enough. holding for grass shrimp. The team also subjected the cuttlefish to a learning task to assess cognitive performance. Cephalopods first learned to associate a visual symbol with a specific prey reward, and then the researchers reversed the situation so that the same reward was associated with a different symbol.

The results: “The cuttlefish in the present study were all able to expect the best reward and tolerated delays of up to 50-130 seconds, which is comparable to what we see in large-brained vertebrates such as chimpanzees, crows and parrots, “says Schnell. Additionally,” The fastest cuttlefish to learn both associations [with the food reward] were better for exercising self-control. “

Humans may have developed the ability to delay gratification as a means of strengthening social bonds, thereby benefiting the species as a whole. In monkeys, corvids, and parrots, the evolutionary engine could be related to their use of tools and food storage (caching behavior), as well as social bonding. But cuttlefish do not use tools or store food, and they are not a social species. On the contrary, the cuttlefish seems to have developed this link between self-control and cognitive performance via a completely different evolutionary path – an example of convergent evolution.

“The cuttlefish spend most of their time camouflaging, sitting and waiting, punctuated by brief periods of foraging,” Schnell said of his working hypothesis on how cephalopods developed this ability to control oneself. “They break the camouflage when they feed, so they’re exposed to all the predators in the ocean that want to eat them. We believe that deferred gratification may have evolved as a byproduct of this, so cuttlefish can optimize foraging while waiting to choose a better quality. food.”

DOI: Proceedings of the Royal Society B, 2021. 10.1098 / rspb.2020.3161 (About DOIs).