Self-Control in Crows: Can They Wait for a Better Prize?

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In a now-famous experiment, researchers placed a marshmallow in front of a child and told them that they could eat the marshmallow now, or, if they waited 15 minutes, they could have two. The researcher then left the room. If the child couldn’t wait for 15 minutes they could ring a bell to alert the researcher, and then they could eat the marshmallow. But if the child held out for the full 15 minutes, the researcher returned and gave them a second marshmallow.

Photo courtesy of ScienceNews.

Fifteen minutes is a heck of a long time to stare at a marshmallow you’re trying not to eat. I don’t know about you, but I’d fail this test! The researchers kept in touch with the kids who participated in the experiment. They found that kids who were able to endure the torturous 15 minutes in order to get two marshmallows instead of one, tended to do better in school and show success in other areas as well.

Psychologists use the fancy name delayed gratification to refer to this ability to wait for a better result. Delayed gratification is a form of self-control, and it is an important building block for things such as decision making and future planning. Kids tend to get better at delayed gratification as they grow older: 5-year-olds are generally better at waiting for two marshmallows compared to 3-year-olds.

Are other animals, besides humans, capable of delayed gratification? It might be no surprise that monkeys and great apes like chimpanzees are able to wait for a better result. In some cases, they even held out longer than adult humans! One species that shows great potential for delayed gratification is New Caledonian crows. They are impressive little tool-users, often using twigs to fish grubs out of logs. Given their incredible problem solving abilities, are they also able to wait for a better prize?

New Caledonia is an island off the coast of Australia:

Photo courtesy of Encyclopedia Britannica. For more information on New Caledonia, look here.

A group of scientists travelled there and caught nine wild New Caledonian crows using nets. The scientists kept these crows in a large aviary during the experiment. The crows were given the names Jupiter, Mars, Triton, Neptune, Io, Mercury, Venus, Uranus, and Saturn. Then, once the experiment ended, they set all the crows free where they were originally caught.

First, the scientists had to find a prize for the crows that the crows really liked. It turns out that they don’t mind apple slices but they really like pieces of meat. The scientists kept this in mind for their experiment. (The scientists didn’t feed the crows marshmallows. Do crows even like marshmallows? I’m not sure…but marshmallows would be a terrible thing to feed crows anyway! Much better to offer them food similar to what they would find in the wild.)

The contraption that the scientists used was quite cool. It was a large, round platform that rotated by remote control. The scientists placed the platform in a clear plastic box with an opening on one side, so the crows could only grab something off the platform if it was right in front of them.

The platform that was used to test delayed gratification in New Caledonian crows. It is enclosed in a plastic box, and crows can only grab something from the open end. In this photo are two objects to show where the food was placed. In this instance the crow could access the object in front, but could not access the object in the back until the platform rotated. Bottom centre of the photo is a large stick that was a perch for the crows. Photo courtesy of Animal Cognition journal.
A crow waiting to snatch something off the platform. Photo courtesy of Animal Cognition journal.

For the test, the scientists placed one piece of meat in one spot on the platform, and a pile of several pieces of meat in a second spot on the platform. They then left the aviary to let the crow swoop down to investigate. (The crows were very shy of people. They only checked out the platform if no one else was in the aviary with them.) When the crow was perched on the branch in front of the platform, a scientist activated the platform by remote control. After five seconds, the one piece of meat appeared in front of the crow, ready to be snatched up. However, if the crow waited fifteen more seconds, then the one piece of meat would have passed by and instead, the pile of meat would be there for the taking. The crow could only make one choice: grab the one piece of meat that was immediately available, or wait and grab the pile of meat. Once the crow made its choice, a scientist entered the aviary, the crow was spooked and flew away, and the experiment ended.

Remember how crows preferred meat over apple slices? Well, in a second test, the scientists put apple slices in position 1 and pieces of meat in position 2 (which rotated past, 15 second later). So the crows could take the less-liked food right away, or they could wait for the better-liked food.

So, what happened? In every case, the crows could pick one of two choices: the food immediately in front of them, or the food that took longer to arrive. If the crows just chose at random, we would expect them to choose the food immediately in front of them 50% of the time, and the food that took longer to arrive the other 50% of the time. It turns out, crows picked the bigger pile of food, and the meat over the apple slices, well above 50%. They certainly showed the ability to delay gratification. Interestingly, they were “better” at delaying gratification during the test with the apple slices versus meat, compared to the test where one piece of meat was pitted against a pile of meat. In other words, they were better at choosing between quality versus quantity. We’re not sure why that is.

Monkeys have also been tested with a similar set-up, where if they wait fifteen seconds, they can grab a better prize off the platform. These crows seem to be in league with those primates! And also, arguably, with humans. What would happen if the delay was increased? Are crows able to hold out longer for more meat, just as the kids did for their marshmallows? It remains to be seen!

Want to learn more about the amazing things that crows can do? Check out this fantastic book:


Miller, R., Frohnwieser, A., Schiestl, M., McCoy, D. E., Gray, R. D., Taylor, A. H., & Clayton, N. S. (2020). Delayed gratification in New Caledonian crows and young children: Influence of reward type and visibility. Animal Cognition, 23, 71-85.