Cuttlefish, like their nearest relatives octopuses and squid, are astonishingly intelligent. They've proven this again by delaying gratification in return for a greater reward.
In 1972, Professor Walter Mischel conducted a now-famous test, putting a marshmallow before a child between three and six years old, telling them he was going to leave the room – but if the food survived his absence, they could have two instead. Mischel then followed up his subjects as adults and found those who held on for the greater prize were generally more successful in life. Ironically Mischel's interpretation of the reasons for this relationship may be wrong for people, but right for marine mollusks.
Applying psychology tests originally devised for children to non-human animals is a growing field, revealing that capacities that appear to go together in humans can diverge in other species.
Dr Alexandra Schnell of Cambridge University taught cephalopods the marshmallow test by first learning the preferences of six common cuttlefish (Sepia Officinalis) between three foods. Schnell then put the cuttlefish in tanks with two chambers, teaching them if they approached one chamber the food in the other would be removed. Once the lesson was learned, less preferred crab was put in one chamber and, after a delay, a more preferred shrimp in the other. Subjects that could resist the crab earned the shrimp.
Schnell reports in Proceedings of the Royal Society B that cuttlefish would wait 50 to 130 seconds for shrimpy delight, but were not all equally patient. “The cuttlefish that were quickest at learning both of those associations were better at exerting self-control," Schnell said in a statement.
Social species require some level of delayed gratification, giving up their immediate interests to assist others for a long-term return. Nevertheless, only great apes, parrots, and members of the crow family have passed tests like this before, despite experiments with many other species. Cuttlefish aren't collaborative, so it is not clear why they've developed this capacity. Schnell proposed it may be a by-product of their hunting strategy.
"Cuttlefish spend most of their time camouflaging, sitting and waiting, punctuated by brief periods of foraging," Schnell said. "They break camouflage when they forage, so they are exposed to every predator in the ocean that wants to eat them. We speculate that delayed gratification may have evolved as a byproduct of this, so the cuttlefish can optimize foraging by waiting to choose better quality food."
It's just two months since another team reported that cuttlefish learn to adapt their hunting to play the odds. While the similarity to Mischel's work was noted, that study wasn't designed to resemble the famous experiment, testing gambling capacity rather than delayed gratification.
A new generation of psychologists has pointed to flaws in Mischel's conclusions. He assumed it was the children who showed a capacity for delayed gratification that caused their subsequent success in life – for example, by staying longer in education. However, subsequent research revealed children growing up in unstable environments were less likely to pass the test, sometimes making entirely rational decisions based on their circumstances. If you are used to adults making promises they don't keep, why believe a stranger telling you there will be two marshmallows at some unspecified point in the future? Growing up to not fulfill your dreams can be at least as much about having started from a rickety platform as any psychological failure. Schnell's cuttlefish faced no such inequality in training.
The marshmallow test retains its power as a metaphor, including for society as a whole. Can we, collectively, not consume things we want now, in order there be abundance in the future? If not, perhaps cuttlefish will inherit the Earth.