Measuring intelligence in animals is a tricky thing. For one thing, we often measure how intelligent an animal is based on how much they can act like us and how well they can please us. I have a feeling if we applied that same measure to our children, geniuses would fall to the bottom of the pile! Which brings me to another interesting observation- if the one or two individuals from a species test well, they are exceptions, if they test poorly, the whole species is doomed to the dunce cap. Does that really make sense?
Border Collies are listed as the most intelligent dog, and having grown up with them, I hate to argue! However, while Gwen, a chihuahua is not as trainable as most Border Collies (she does it on her time only), I certainly don't get the feeling there is any less going on up there. In applying this to parrots you can very easily substitute Border Collie with African Grey. I can't say how many times I have seen someone ask whether x species of parrot could possibly be as intelligent as African Greys, or say that no other species of parrot is as intelligent as African Greys. This, I firmly believe, is untrue. You can have very smart and very, er, not so smart, African Greys just as you can with any other species of parrot, and just as you do with people.
This inevitably brings me around to Alex. Dr. Pepperburg took care to make sure Alex was random, so people would not think he was exceptional. And looking at what many other people's greys can do without the intense training Alex had, I think it is very likely he was not. What I also think should be said, though, is that just because Dr. Pepperburg was able to show how intelligent African Greys are does not mean other species are not as smart. One thing that does set greys apart is their love of language and their learning style. My budgies can do and learn amazing things, and just because they have much shorter attention spans, does that make them necessarily that much less intelligent? In fact, Dr. Pepperburg said herself that she chose greys for their language abilities, but she does not think that means they are heads and tails smarter. She even mentioned budgies, but said their shorter attention spans and shorter lifespans rule them out as good subjects. She went on to mention the different (generalized) learning styles of a few species, saying others could do things that Alex did not. Personally, and this just came to me now, I think ekkies would make fantastic subjects as well. They have both the language and intense, long attention spans. Or some of them anyway, Claudia loves to talk like any diva, but as for intense learning........
We have barely scratched the surface of the intelligence of the cephlapods, such as octopus and cuttlefish. The things we know they can do are sometimes even far beyond what we can. And yet, if you show them a mirror, they don't recognize themselves. Both elephants and dolphins have been proven to recognize themselves in mirrors. This is part of being self-aware. I am really not sure whether my parrots can do this or not, and I know no one has proven that other parrots can. I know Chester doesn't recognize himself, and on the others I am unsure. Until I can think of a way to test that (they put an x on the elephant's face, and he tried to get it off himself, not the elephant in the mirror) I will just have to leave it at that!
The point? I am always fascinated by animal intelligence research and findings. What you conclude from them, though, will vary a great deal with your "definition" of intelligence. One thing for sure, though, is that intelligence is not a linear scale, with ourselves at the top and the sponge (for example, nothing against sponges) at the bottom, and little marks along the way showing what abilities are required before you reach the next level.