Calling someone a "birdbrain" is not intended as a compliment. But some birds seem pretty smart. Parrots, for example, can mimic human speech. But does a parrot's ability to repeat human words and phrases mean that it can actually think and reason?

Scientists have debated this question for many years. Some believe that parrots can be trained to express abstract concepts. Others say that while their ability to mimic speech makes it seem as though parrots can really think, in the end they're more like tape recorders, thoughtlessly repeating what they hear.

One firm believer in parrot thoughtfulness is Irene Pepperberg, a researcher associated with Harvard University. Her African Gray parrot, Alex, not only has a sizeable vocabulary but has demonstrated the ability, according to Pepperberg, to think abstractly.

In a typical experiment, Pepperberg will ask Alex to identify a particular object, say a blue square, from among a jumble of toys on a tray. According to Pepperberg's reports, which she has documented on video, Alex can use his understanding of the concepts "blue" and "square" to pick out the correct object, say how many there are, and even can report "none" if there aren't any.

While some scientists are willing to concede that Alex's abilities indicate primitive thought processes, they do not agree that Alex can reason in any complex sense. Instead, they claim that Alex has been trained to perform very sophisticated imitations.

So why should we care whether or not parrots can really think? We tend to see conscious, complex thought as separating humans from other animals. The existence of other thinking animals might urge us to reconsider our innate superiority. And that's something worth thinking about.