We have long known that ravens are no birdbrains.
They have been spotted caching food for later, gathering string to pull up hanging food and even trying to deceive one another.
A study published today in Science adds an especially impressive twist: Ravens can plan for future needs that they never encounter in nature, suggesting intelligence may arise predictably from conditions that occurred multiple times across the tree of life.
The new study was led by Mathias Osvath, a cognitive zoologist at Lund University in Sweden, and graduate student Can Kabadayi. The pair replicated a series of experiments previously used to test apes’ planning abilities, this time using ravens.
The ravens were first taught to use a stone to knock a food pellet out of a puzzle box. The next day, without the box present, the birds were offered a choice between the stone tool and “distracter” objects—toys too light or bulky to use as tools.
The box would then be brought back 15 minutes after the selection. Despite the delay, the ravens chose the correct tool nearly 80 percent of the time, and successfully used the tools they selected 86 percent of the time.
The birds performed almost as well when they had to give an experimenter a bottle cap in exchange for a piece of food. The birds almost always selected the bottle cap over distracters, even though they would have to wait 15 minutes to barter with it.
The preference for soon-to-be-useful items persisted when the ravens had to pass up a smaller treat in favor of either the tool or the bartering token—and even when they could use each item only after a 17-hour delay.
The ravens’ stellar performance, in some cases exceeding that of great apes and four-year-old children, has many scientists excited. Previous experiments on birds’ planning abilities have been criticized for examining behaviors the animals perform in the wild, such as storing food, for which they could have evolved specialized skills.
“There was no real proof that [ravens] actually can transfer a cognitive ability in future planning to other behaviors,” says Markus Böckle, a professor of psychology at the University of Cambridge and co-author of a related commentary in Science who was not involved in the study.
“This is the first time we have clear evidence in any animal” besides humans.
The results have important ramifications for the evolution of intelligence.
They imply the “capacity [for flexible planning] may have evolved at least twice in separate lineages of animals that split around 320 million years ago,” says Jonathan Redshaw, a cognitive psychologist at The University of Queensland in Australia.
To comparative psychologist Alex Taylor of the University of Auckland in New Zealand, the finding also implies something much broader: “It suggests that planning arises predictably from similar types of selection pressures, and it’s not…some kind of one-off that just cropped up [once] in the ape lineage.”
Böckle hypothesizes that complex planning in ravens evolved thanks to two factors similar to those that shaped ape intelligence. First, ravens live complex social lives, flocking by the thousands for up to 10 years before establishing a territory with a mate.
Second, their food source—carcasses—is rare and ephemeral, so using it well takes clever planning. Böckle guesses the birds’ planning ability emerges from the combination of those social and technical constraints.
But not everyone is fully convinced by the results. Even Böckle wonders how strongly they generalize beyond the five hand-raised birds in the study, which could be “the Albert Einsteins [of] the raven world.”
Taylor and Redshaw see a more fundamental issue: The ravens could simply have learned to associate the tool with top-notch food. Experiments in apes have ruled out this possibility by offering a second tool, which would retain any positive associations but offer no additional benefit.
Redshaw also suggests testing associations by visibly destroying the reward box, rendering the tool useless. Taylor predicts the findings’ openness to interpretation will make them “quite controversial.”
Still, the study at least suggests a powerful capacity for planning, and opens up the possibility of comparing tool use and planning among vastly different species.
Future studies, in addition to ruling out confounding explanations for the birds’ behavior, will build up a more complete map of related species’ abilities.
And although it is even harder to peer into the mind of a bird than that of a human, scientists hope to explore the neurobiological mechanisms by which the birds can plan. It is not yet clear, for example, whether birds are mentally simulating or pre-experiencing the future the way humans seem to do.
When we do manage to put the birds in brain scanners, we may continue to discover that we are less unique than we think.