Researchers first discovered the link between self-control and intelligence not in humans or chimpanzees, but in cuttlefish.
The study was conducted at the Marine Biological Laboratory (MBL) in Woods Hole.
The authors of the paper used an adapted version of Stanford’s “marshmallow test”, where children were given a choice: immediately eat the reward (1 marshmallow) or wait to get more.
Cuttlefish in the new study were able to wait for the best reward and tolerated up to 50-130 seconds. This is comparable to the results of large-brain vertebrates such as chimpanzees, crows, and parrots. The cuttlefish that waited the longest for food also showed the best cognitive ability on training tests.
In this experiment, cuttlefish were trained to associate visual cues with food rewards. Then the situation changed, and the reward became associated with a different signal. The cuttlefish that learned both of these associations the fastest were the best in control.
Finding this link between self-control and learning in a species outside the primate lineage is an example of convergent evolution, where completely different evolutionary processes lead to the same cognitive trait.