There was once an extremely intelligent West African Gray Parrot called Alex.

Alex was a famous parrot not only able to talk rather fluently but, it now appears, also able to count objects and perform numerical calculations, according to an article published in Animal Cognition, by Irene Pepperberg.

Dr. Irene, who trained Alex, reports her charge had great mathematical skills and was able to add two Arabic numerals and the total number of objects under three cups.

She performed 12 trials asking Alex to add two Arabic numerals and amazingly he gave the right answer nine times. When she presented him, sequentially, with three sets of objects hidden under three cups, Alex gave the correct answer eight out of ten times.

Incidentally, the discovery that Alex was able to add objects was an accident.

She once presented him with a tray containing four green, three red and five blue blocks. She asked Alex: "what colour five?" and he replied: "blue". However, when she tested a second parrot (Griffin), hoping he could equate sound sequences with quantities, she made a rather startling discovery.

She played two clicks, hoping Griffin would reply. Unfortunately, he didn't. Instead, when she clicked twice more, Alex, who was in the same room, said: "four". Amazed, she clicked twice more and Alex said: "six", said a report in Nature.

Alex died in 2007 of unknown causes.

"I wish that Alex had lived longer and I think this is an important study because it showed what he could do and where he was going," Nature quoted Dr. Pepperberg as saying.

Alex is one of two non-humans - the other being a chimpanzee named Sheba - who have so far been identified as showing mathematical abilities.

Click here to check Alex's ability to count objects.