Everyone knows parrots can speak simple sentences. But most scientists have assumed parrots aren’t capable of more complex forms of language; that’s the province of higher-order animals like humans and chimps. In the last few years, though, the MIT professor Irene Pepperberg has been conducting some rather amazing experiments with her pet grey parrots. One of them, Alex, has been able to grasp some incredibly nuanced uses of language, as Pepperberg desribes in an interview at The Edge:

We test him not only through direct questions about these concepts (e.g., “What color bigger?” for two differently sized and colored blocks), but also by using questions that involve complex structures—recursive phrases or conjunctive, recursive phrases—such as, “What object is green and three-corner?”; he answers all these questions with about 80% accuracy. We think the reason he doesn’t achieve 100% accuracy is boredom; he seems to get tired of repeatedly telling us about colors and shapes and materials. For example, he sometimes will state every color but the correct one, behavior that suggests that he is carefully avoiding the right answer; statistically, he couldn’t do that by chance.

Check out the rest of the interview; it’s pretty stunning. There’s more info at The Alex Foundation, Pepperberg’s research institute on the “communication and intelligence of parrots.” Ultimately, she sums up the parrots thusly:

What I’ve tried to explain to parrot owners is that what they have in a cage in their living room is a creature with the sentience of a four- to six-year-old child. I try to convince them that you can’t just lock it in a cage for eight hours a day without any kind of interaction.