Can Animals Delay Gratification?

In daily life, we repeatedly have to decide whether we prefer something immediately – thus, the bird in the hand – or are willing to wait for something better – two birds in the bush. To solve this problem, and potentially get something better than we have now, we need patience. But on the other hand, we cannot be 100 percent sure that the better thing will really occur, i.e. whether we will really be able to catch the two birds in the bush.

Walter Mischel investigated this dilemma in his famous "marshmallow test" with children. They could decide whether to eat one marshmallow immediately or delay their satisfaction and receive two. He found that four-year-olds would wait about 6 to 10 minutes for the delayed reward – but there were huge individual differences in the amount of time a child is willing to wait. It seems that the longer subjects wait in such experiments, the better they are able to cope with frustration and stress and resist temptation. Indeed, there is some evidence that the ability to control impulses and delay rewards is a reliable predictor of later academic success and a number of positive personality traits (Mischel, 2014).

Animals Can Delay Gratification, Too

Animals face similar challenges and are often forced to decide between a bird in the hand or two in the bush. For example, imagine being a chimpanzee feeding on fruits in a tree together with your troop. When a colobus monkey passes by, you will have to decide whether to leave the fruits you’ve already found in order to hunt after the larger gains of monkey meat, but the success of the hunt is uncertain and largely depends on whether your pals join the hunt. Should you fail and return to the fruit tree empty-handed, the fruits might be gone, too. There are various other situations in the wild that require animals to decide whether to keep the bird in the hand or go for the two in the bush; just think of animals that cache food or travel long distances to high-quality food patches.

Scientists have used two main tasks to investigate the ability of animals to delay gratification. In the exchange test, subjects are given an immediate reward as a trade currency and can choose to keep it intact through a delay, later exchanging it for a better reward, or to finish the trial by starting to eat. The value of the delayed reward can surpass the immediate one either in quality – like in our chimpanzee example (fruit versus meat) or quantity. The second task is the accumulated test, in which the rewards mount up in quantity in the course of the delay. When subjects make the choice to eat, they discontinue the accumulation of the food – quite similar to the original marshmallow test.

So, how do different animal species perform in these tasks? As you might expect, our closest living relatives, bonobos and chimpanzees, exhibit a high degree of patience (Rosati et al 2007). But surprisingly, the apes even outperform humans when the task is about food rewards (although humans are more willing to wait for monetary rewards). Bonobos also seem to have a pretty good grasp on the social aspects of the situation: In one study, they were tested with a reliable and an unreliable experimenter. They then waited less often with the unreliable person (Stevens et al 2011).

Patience May Not Be Unique to Humans

Besides apes, monkeys, rats and birds can also solve the task. Goffin cockatoos are able to bridge delays of up to 80 seconds for a preferred quality of food and up to 20 seconds for a higher quantity. Keas wait up to 160 seconds in the food exchange test. Parrots and New Caledonian crows have also been shown to delay their gratification for a better reward (Miller et al 2020). Carrion crows and ravens can control impulsive behaviour, even over prolonged periods of up to 10 minutes, no matter whether they are tested in the exchange test or in the accumulation test (Hillemann et al 2014).

In canids, researchers found an interesting difference in the performance of domestic dogs compared to their wild cousins, wolves. Both species were tested in the exchange test, in which they had to wait for a predefined delay duration to exchange a low-quality reward for a high-quality reward. Dogs outperformed the wolves, waiting an average of 66 seconds versus 24 seconds for the wolves (Range et al 2020). One possible explanation for this is domestication, i.e. that dogs have been selected to live in the human environment, and are therefore have become better at self-control. On the other hand, it is feasible that wolves in the wild have learned that sometimes one bird in the hand is a safer bet than hunting the two in the bush.

Patience is sometimes thought of as a uniquely human personality trait, something that separates us from the animal world of instincts. But if birds and mammals can delay gratification for future rewards, perhaps patience is more widespread – and important – than we thought. A recent study has shown that cuttlefish maintained delay durations of up to 50 to 130 seconds (Schnell et al 2021). I wonder if Mischel would have guessed that one day a mollusk would pass his marshmallow test.