For centuries, we told ourselves that we are special — that what separates humans from animals is our ability to reason.
But that belief has been increasingly undermined given evidence showing apes also have the intelligence to use tools, solve complex problems and even plan for the future.
Now the latest indignity: Ravens can do it, too.
On a rural research farm in Sweden, working with birds he raised from hatchlings, cognitive zoologist Mathias Osvath recently taught five ravens how to use a tool to open a puzzle-like box containing a treat. He then put his birds through a battery of tests in which they had to choose the tool, despite the temptation of a more immediate goody with the box nowhere in sight.
The birds didn't bite. Only when the box was brought back did they use the tool they had been saving to secure the better reward — demonstrating self-control, advanced reasoning and planning.
“It’s not just the fact they have these skills independently. But to use them together to make these complex decisions, that’s what makes it so amazing,” said Osvath, in Lund, Sweden.
He compared his subjects' calculations to the sophisticated decisions that humans make daily.
“Say you’re planning a trip to London, and you know how often it rains there. So you bring an umbrella, even though it’s not raining now where you are. That’s what we are talking about here, planning based on past experience,” Osvath said.
His study — published Thursday in the journal Science — is the latest in a growing body of work from cognitive zoologists that is tearing down assumptions about the limits of animals’ ability to reason.
Some of the more recent work has built on a 2006 study by researchers in Leipzig, Germany, who used puzzle tests such as Osvath’s raven experiment to show that apes could use tools and do planning. But scientists working with birds have long suspected some winged creatures could match the intellect of apes, particularly the wickedly smart ravens, crows and jays — members of the corvid family.
Several studies tried to measure and document those birds’ cognitive skills, mainly by focusing on their obsession with hiding food. Some found that ravens hid their food more quickly if they thought they were being watched. In other tests, scrub jays even moved their hidden food to a second spot once they realized they were being watched, in an apparent effort to ward off potential thieves.
Corvid scientists contended such behavior proved some birds have a cognitive awareness of what others might know or intend, as well as the ability to plan for future consequences. Critics shot down such conclusions, saying the birds' reaction could be simple, instinctive responses to visual cues.
“It was a big argument, because it was difficult for some to imagine that birds could do these things, too,” said Thomas Bugnyar, a cognitive professor at the University of Vienna who has studied ravens for 20 years but was not involved in Osvath’s research. “People kept looking for holes or possible alternative explanations.”
Stepping squarely into the fray, the Swede set out to design a study to definitively prove the birds’ advanced abilities to reason.
Back in the mid-2000s, he had conducted some of the very studies hailed as proof of planning in apes. One of his most widely publicized (and amusing) reports, in fact, documented how a male chimpanzee at a Swedish zoo would leisurely collect stones and hide them in strategic places during early-morning hours just so that he could later hurl them at gawking visitors.
Osvath now hoped to do the same for ravens.
To conduct his experiment, he raised a group of ravens for five years. He witnessed their intelligence up close — playing games with them, watching as they developed complicated relationships with his graduate students. (One male raven particularly loved pecking his least favorite students on the head.)
Osvath had to modify the tool-based experiments he and others had conducted on apes, given birds' lack of opposable thumbs. Instead of the sticks or drinking straws used with apes, the ravens got small rocks as tools to open the boxy contraption. For their reward, he provided a juicy, meaty dog kibble that they seemed to love.
In the end, the ravens matched the primates in every respect. On tests in which they had to barter for their reward by trading a specific token, the birds outscored the apes and even outperformed 4-year-old humans.
In an accompanying perspective, two University of Cambridge cognitive scientists called Osvath's study “compelling evidence.” They wrote, “These results suggest that planning for the future is not uniquely human and evolved independently in distantly related species to address common problems.”
Based on past experiences, Osvath expects some people may be upset by his new study.
“When it comes to what animals can do compared to humans, there are those who cling to cognition as uniquely human,” he said in a phone interview, as his ravens squawked audibly in the background. “I think it has to do with religion, with this argument over whether animals have a soul or free will, and whether we are unique in the world.”
This obsession with human uniqueness, however, misses the entire goal of research into how animals think.
“Yes, we humans are incredibly unique beings,” Osvath said, “but if that’s all you focus on, you miss the wider question of cognition and its amazing place in nature. The real question of cognition is, how did all of us — humans and animals — go from just an accumulation of matter to beings with thoughts? That is one of the most astounding things in this universe.”
On that central question, he and others working with corvids believe their work poses major new questions given how birds and mammals went their separate ways on the evolutionary road some 300 million years ago. So did corvids and apes arrive at their sophisticated intelligence in totally different ways or based on similar factors and principles?
For evolutionary biologists, that and related questions loom large, with ramifications for everything from how intelligent life formed on Earth to whether extraterrestrial life might look or think like us.
“These are the real questions we should be asking about nature,” Osvath said. “Instead of just focusing on ourselves as humans, we should see ourselves as part of this world. If this study changes even one or two people’s minds about that, I will be happy.”