All of us know how tough it can be to delay gratification. But human civilization was built around our supposedly unique ability to plan—to anticipate future needs and sacrifice now to reap the rewards later. Apes knocked us off our special perch nearly a decade ago when they showed that they, too, can plan for future events. Now, a new study on tool use and bartering in ravens reveals that these clever birds are joining the club—suggesting that the ability to plan for the future must have evolved at least twice.
“This experiment provides an important puzzle piece for understanding the evolution of intelligent behavior,” says Markus Böckle, a comparative biologist at the University of Cambridge in the United Kingdom who was not involved in the work.
Planning is the ability to think through future events taking place at a different location. Ten years ago, Mathias Osvath, a cognitive biologist at Lund University in Sweden, designed a series of tests to measure whether other primates were planners. Great apes—like chimpanzees—passed. Monkeys failed. About the same time, researchers noticed that birds known as corvids—which include jays, crows, and ravens—also showed signs of planning. Studies over the last 20 years have revealed that these birds can use tools and deliberately hide their food caches. Many saw close parallels between human, ape, and bird brains. But critics argue that food caching is a specialized behavior that doesn’t represent a general planning ability. To prove that general ability, they want the animal to show it can plan even in a situation that it doesn’t usually encounter.
So Osvath and his graduate student Can Kabadayi set out to settle this question by testing the birds in the same way as the apes, this time making sure that they incorporated behaviors that the birds did not normally exhibit. For example, ravens are not regular tool users, and they do not barter with each other, like some jays or crows. So the researchers first taught five ravens to use an oblong stone tool to open a box with dog kibble in it. The birds also learned to trade that tool for a token—a plastic bottle cap—that would get them an even better reward. Over several experiments the researchers switched up the rules of their game, changing when the rewards were present and what the birds had to do to get them.
The ravens consistently picked the right tool not only when the reward box was present, but also when the box was missing—for up to 17 hours, Kabadayi and Osvath report this week in Science. In one experiment, the birds were offered an immediate reward—a small piece of kibble—in addition to the tool and several other objects. Almost three-quarters of the birds picked the tool, even though they had to wait 15 minutes to use it to get a bigger piece of kibble. In terms of self-control, “they can do just as good or better than the great apes,” Osvath says.
Then, the researchers showed that the birds were thinking about the consequence of this delayed gratification—something that has been demonstrated so far only in people. When the birds had to wait just a few seconds for access to the reward box, they opted to wait 100% of the time, they report. “When they have a short delay, they are much better at self-control,” Osvath says.
“It’s the clearest evidence for future planning in a nonhuman animal,” says Nathan J. Emery, a cognitive biologist at the University of London who was not involved with the work.
These tests show that the ravens have the ability to recognize and remember the tool, anticipate its utility, and show self-control in the face of more immediate temptations, all key components of planning. “They combine these skills in a similar fashion as great apes,” Osvath says. However, he adds, just because the end result is the same doesn’t mean that the birds and the apes are going through the same cognitive processes.
That’s the opinion of Jonathan Redshaw, a comparative psychologist at the University of Queensland in Brisbane, Australia. It’s possible, for example, that these results arose simply because the ravens learned to associate the tool or token with a certain reward and always chose them, he says. That’s not the same as complex planning for the future, in which the planner shows flexibility in taking action to meet future demands. He suggests the team in Sweden see whether the ravens continued to select the same tool after seeing the reward box destroyed. If they gave up picking the tool, that would show they really were planning for the future and not just in the habit of picking the right tool to get a reward.
If the birds do prove to have these capabilities, then future planning must have evolved at least twice, Osvath says. That’s because birds and mammals began evolving their separate ways some 320 million years ago. It was not “an evolutionary one-off that occurred once due to a quirk of history,” says Alex Taylor, a comparative psychologist at the University of Auckland in New Zealand. Further studies into bird and mammal cognition could help researchers gain a better understanding of what it takes—in terms of brain anatomy and function—to anticipate and take into account what might happen next.