Whether it’s calculating your risk of catching the new coronavirus or gauging the chance of rain on your upcoming beach vacation, you use a mix of statistical, physical, and social information to make a decision. So do New Zealand parrots known as keas, scientists report today. It’s the first time this cognitive ability has been demonstrated outside of apes, and it may have implications for understanding how intelligence evolved.
“It’s a neat study,” says Karl Berg, an ornithologist and parrot expert at the University of Texas Rio Grande Valley, Brownsville, who was not involved with this research.
Keas already had a reputation in New Zealand—and it wasn’t a great one. The olive-brown, crow-size birds can wield their curved beaks like knives—and did so on early settlers’ sheep, slicing through wool and muscle to reach the fat along their spines. These days, they’re notorious for slashing through backpacks for food and ripping windshield wipers off cars.
To see whether keas’ intelligence extended beyond being mischievous, Amalia Bastos, a doctoral candidate in comparative psychology at the University of Auckland, and colleagues turned to six captive keas at a wildlife reserve near Christchurch, New Zealand. The researchers taught the birds that a black token always led to a tasty food pellet, whereas an orange one never did. When the scientists placed two transparent jars containing a mix of tokens next to the keas and removed a token with a closed hand, the birds were more likely to pick hands dipped into jars that contained more black than orange tokens, even if the ratio was as close as 63 to 57.
That experiment combined with other tests “provide conclusive evidence” that keas are capable of “true statistical inference,” the scientists report in today’s issue of Nature Communications.
The researchers also showed the keas two jars that each contained an equal number of black and orange tokens. But the experimenter could only reach the tokens located above a solid barrier. Most of the kea correctly chose hands that had reached into the jar with the greatest ratio of black tokens above that divider, showing that they based their predictions solely on physical information—the number and relative quantities of tokens above the barrier.
In a final test, keas were more likely to take tokens from a researcher who showed a bias for black tokens—that is, one who always reached for black tokens even though there were more orange in the jar. Previously, only humans and chimpanzees were known to integrate this type of social information to make predictions.
The findings indicate that keas, like humans, have something known as “domain general intelligence”—the mental ability to integrate several kinds of information, the researchers argue. That’s despite the fact that birds and humans last shared a common ancestor some 312 million years ago and have markedly different brain anatomies. Previously, cognitive researchers have argued that domain general intelligence requires language.
Irene Pepperberg, a comparative psychologist and expert on parrot cognition at Harvard University, is skeptical. Pepperberg, who worked with the famed parrot Alex for 31 years, says the kea showed “some intuitive understanding, but not … real statistical knowledge.” In her view, the study could not prove the birds understand in detail how the proportions of tokens in a jar influence the probability of a reward.
If kea really do have the abilities the study suggests, there’s a good reason they evolved it, Berg says. Animals with even basic statistical and predictive skills should be able to estimate amounts of food or the availability of mates, and so end up with more offspring and evolutionary success, he says. In other words, if you’ve mastered Statistics 101, you’re likely to succeed in the game of life.