USA: Intelligence Test Smart Cuttlefish Pass the Marshmallow Test
Cuttlefish can delay gratification — wait for a better meal rather than be tempted by the one at hand — and those that can wait longest also do better in a learning test, scientists have discovered. This intriguing report marks the first time a link between self-control and intelligence has been found in an animal other than humans and chimpanzees.
Woods Hole/USA — The marshmallow experiment was a study on delayed gratification conducted for the first time in the 1970s. In this experiment a child is offered a choice between one small but immediate reward, or two small rewards if they waited for a period of time. Researchers at the Marine Biological Laboratory (MBL) used an adapted version of the Stanford marshmallow test. 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.
Cuttlefish that could wait longer for a meal also showed better cognitive performance in a learning task. In that experiment, cuttlefish were trained to associate a visual cue with a food reward. Then, the situation was reversed, so the reward became associated with a different cue. “The cuttlefish that were quickest at learning both of those associations were better at exerting self-control,” says lead author Alexandera Schnell.
Why cuttlefish have evolved this capacity for self-control is a bit mysterious. Delayed gratification in humans is thought to strengthen social bonds between individuals — such as waiting to eat so a partner can first — which benefits the species as a whole. It may also be a function of tool-building animals, who need to wait to hunt while constructing the tool.
But cuttlefish are not social species, and they don't build tools. Instead, the authors suggest, delayed gratification may be a by-product of the cuttlefish's need to camouflage to survive.
“Cuttlefish spend most of their time camouflaging, sitting and waiting, punctuated by brief periods of foraging,” Schnell says. “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.”
Finding this link between self-control and learning performance in a species outside of the primate lineage is an extreme example of convergent evolution, where completely different evolutionary histories have led to the same cognitive feature.