The birds watched as a researcher took tokens from each jar and held one in each hand, not showing which
held which. In almost every instance, the kea chose the hand that appeared most likely to have selected the
black token. In another experiment, a researcher created a “bias” scenario by only offering black tokens.
When offered tokens from two experimenters, the parrots showed preference for the researcher who only
gave black tokens.
The team wrote in the paper: “Birds last shared a common ancestor with humans at least 312 million years
ago. This result provides evidence that true statistical inference is found outside of the great apes, and that
aspects of domain general thinking can convergently evolve in brains with a highly different structure from
primates.” The findings are published in the journal Nature Communications.