According to new research, ravens are capable of restraint.

Researchers found that ravens will ignore a treat if they know they can get a better one later, implying that the birds possess significant self-restraint. It’s compelling information and more evidence of the incredible intelligence of corvids.

Ornithologists have long known that corvids, a group that includes ravens, crows, and blue jays, are the most intelligent birds. As far back as the 19th century, bird watchers observed corvids outsmarting humans and other birds with their advanced problem-solving capabilities.

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Throughout the 20th and 21st centuries, researchers tested the limits of ravens and their relatives to determine their functional intelligence. The findings are mind-blowing.

For instance, a study published in Animal Behaviour showed that ravens can remember the faces of human trainers as well as which ones dealt more fairly with the birds. During an experiment in which ravens could exchange bread for cheese, one researcher would take the bread but refuse to give the cheese. The ravens quickly learned to recognize the researcher’s face and avoided her in favor of other researchers, who delivered on their part of the deal.

Ravens have also learned to use rudimentary tools and complex processes to get food.

A 2007 experiment had ravens sit on a perch with a piece of food dangling on a string below them. To get the food, the feathered subject had to pull up the string, make a loop, put its foot on the loop, and repeat the process six times, slowly reeling in the treat.

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Other animals could be taught that same process, researchers found, but the ravens figured it out on their own.

“These birds have never seen string before or encountered meat hanging this way, yet they worked out exactly what they needed to do to get a treat,” said Brad Heinrich, a researcher in the experiment.

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In the latest study on the subject, published in Science, researchers compared ravens to apes in terms of their ability to use foresight. Can Kabayadi and Mathias Osvath of Lund University taught ravens that choosing a specific token would get them an immediate reward. The scientists also gave the crows a tool that opened a puzzle box containing an even better reward. When given the tool, the ravens had to wait 15 minutes before researchers brought out the puzzle box with the superior treat.

Once the ravens learned these two processes, the researchers gave them a choice.

The birds could either take a token that was good for an immediate reward or the tool that would earn them a better treat 15 minutes later. The test showed that ravens chose the tool 73.8 percent of the time. This suggests the birds remembered that a 15-minute wait would result in a superior treat.

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The experiment tested delayed gratification in a method similar to the famous Stanford marshmallow experiment. In that study, children could either eat one marshmallow or wait 15 minutes and have two marshmallows. The children who had the foresight and willpower to wait for two treats had significantly better life measures (such as SAT scores and body mass index) in follow up studies.

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That doesn’t mean ravens are as smart as children, but they seem to have similar capacities for delaying gratification. The raven study strengthens the case of those who believe that corvids are among the most intelligent animals on the planet. Corvids have beaten dogs and cats in certain tests, and ornithologists consider them the most innovative birds at acquiring food in the wild. A 2004 study focusing on “tool manufacture, mental time travel, and social cognition” put corvids on par with great apes.

As scientists perform more studies, we’re learning that animals know a lot more than we believe. The corvid’s tool-making ability and foresight are impressive, but they might just be the tip of the iceberg of what we’ll learn about animal intelligence.