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  • Alan S Kolok

March 6 Good Science News #8 The Marshmallow and the Cuttlefish


In 1972, psychologist Walter Mischel conducted a test, what has become known as the Marshmallow test, on a number of children. In his study, 4-year-olds were given a choice regarding a treat that they wanted, a marshmallow. On the one hand they could wait 15 minutes after which they would receive two treats, or they could ring a bell and receive a single treat anytime between the beginning of the experiment and its end. It was a classic study of delayed gratification, and Mischel found that the children who could hold out longer also had higher SAT scores, and according to their parents, could plan better for the future and handled stress more effectively.

Now consider the cuttlefish. If presented with a simple choice, crab meat for breakfast, or shrimp, which they like much better for dinner, the cuttlefish chooses to go hungry and wait. Is this an example of delayed gratification? It wasn't very clear, so a second study was conducted.

The second experiment gave the cuttlefish a choice between a live grass shrimp (which they really like to eat) or a piece of raw prawn. Since the cuttlefish had been trained to recognize symbols, (a circle adjacent to a transparent window meant it would open right away, a triangle meant a delay of between 10-130 seconds, and a square meant that the window would not open), the cuttle fish was able to make choices at the buffet.

If the cuttlefish realized (by the shapes next to the window) that the live shrimp would become available to the cuttlefish two minutes after the experiment began, the cuttlefish would ignore the readily available piece of prawn and wait. If the cuttlefish realized that the live shrimp would never be available to them, (again due to the learned shape adjacent to the window) the cuttlefish would eat the piece of prawn straight away. The cuttlefish was making food choices, and when appropriate was displaying classic delayed gratification.

Why would a cuttlefish do that?

Cuttlefish in the wild experience long periods of inactivity, periods where they remain camouflaged and hidden from predators, followed by short bursts during which they feed. When feeding they are susceptible to being eaten by predators, therefore wise decision-making is vital to their survival. Is it better to eat and be susceptible to predators or hide and go hungry? It all depends upon what is on the menu.

Perhaps more striking than the delayed gratification, is the realization of who is doing the choosing. Cuttlefish are molluscs, that is, they are members of the phylum mollusca, a phylum that includes snails, slugs and clams. That’s right, this animal who is displaying the capacity of delayed gratification, in much the same way as a four-year-old, is more closely related to a clam or a snail than it is to us.

Humans, along with other member of the vertebrate phylum, for example crows, great apes and to a lesser degree dogs, all have the capacity for delayed gratification.

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