Beran, who also authored the book "Self-Control in Animals and People," has focused his research on cognitive control and how children and nonhuman primates show self-control. His work encompasses delayed gratification and how both children and primates monitor how much they know or remember and then decide when they need help or seek more information. These activities, he explains, require making a deliberate choice.
Why study this in animals? There are two major reasons, argues Beran. "In itself, the question of self-control and delay of gratification (like the marshmallow test assesses) is a question about animal minds." By engaging in cognitive control, an animal is demonstrating that it is mentally processing the problem it is facing. And researchers can observe and begin to understand the animal's cognitive process.
The second reason is to study other species to better understand who we are. "We want to know if human language is special for delay of gratification, or if big brains are necessary, or culture is required," he says. "To better understand this, we need to see what other species can do."
Can animals pass the marshmallow test? Sometimes, Beran says. But humans do it at levels beyond the imagination of animals. Proof of humans' delayed gratification can be seen in farmers who give fields a year to stay fallow to increase future yields in later years rather than growing a faster yielding crop of less market value. Or stockholders who resist the urge to sell when prices fall, knowing they'll bounce back eventually.
"Chimpanzees are not doing this kind of delayed gratification (that we know of)," Beran says. "But, what it takes to wait five minutes to double your reward is presumably a basic, core process relevant to humans' capacity for extreme delay of gratification."
Beran created a version of the marshmallow test for chimps where they could wait for a better reward (delivered minutes later) or press a button to take a reward immediately. When they had to wait for a better reward (a banana rather than a carrot) they often did. Another test he developed tested whether chimps and other primates would leave an accumulation of food alone if the pile increased the longer it was left alone. Chimps were able to do this, using distraction techniques (like looking at a magazine) to let more candies accumulate.
There are several ways an animal's ability to delay gratification can indicate long-term success and, as a result, survival, Beran says. For example, a monkey wants food that's only available on the other side of an open field of tall grass and he impulsively runs toward it. But in doing so, he may not see a predator in the field and get killed, and thus never pass on his genes. "The hesitant, cautious monkey that pauses to look before moving through the field may see that predator," and survive, he says.
Tool use in animals is another example. To locate nuts, and hammer stones to crack those nuts, and then to hammer until a nut opens to provide calorie-dense food takes more time and effort than simply eating whatever is nearby, like fruit or a plant. "To get something better required waiting longer, and putting in more effort," he says.
Some low-ranking animals wait until more dominant animals have moved away before moving to a food source they have spotted. Had they not waited patiently, the dominant animal would have seen the food they were after and taken it. "To do this requires inhibitory control, and perhaps even some level of strategizing that 'I can get that later, once he has moved away and it is safer to approach,'" Beran says.
In March 2021, results of a marshmallow test with cuttlefish was published, which showed the mollusk was able to tolerate delays of 50 to 130 seconds to get its desired prey (live grass shrimp). It also showed that the cuttlefish able to wait the longest for their favorite foods also performed best during learning tests. This marked the first time a link had been shown between self-control and learning performance in a non-primate animal, the researchers said.
