The final experiments with Alex, an African grey parrot (Psittacus erithacus) who amazed researchers with his language and cognitive abilities, have been published.
The paper, written by Alex's primary trainer Irene Pepperberg, appears in the journal Animal Cognition. It shows that the parrot's mathematical skills, including adding multiple numbers together, rival those of chimpanzees and other non-human primates.
Pepperberg and Alex were at the forefront of avian cognition research. Pepperberg worked with Alex for 30 years before his death in 2007, and published numerous scientific papers demonstrating his surprising intelligence. Alex had gained renown for his ability to learn and voice labels for dozens of different objects and concepts. He could categorize objects by their color, size, material, and quantity, and even understand a "zero-like\" concept. Alex could identify and correctly order Arabic numerals from one to eight, and Pepperberg says he spontaneously learned to equate these symbols with the appropriate number of objects. He could sum two sets of objects (such as crackers or jelly beans) as long as their sum total was six or less.
This new study was designed to further examine Alex's counting and addition abilities. One task involved adding numeric numerals, and the second required the parrot to sum three sets of objects presented one after the other. Both experiments were cut short by Alex's death, but the results are still significant and intriguing.
In the Arabic numeral addition task, Alex was asked "How many total?" In twelve trials, he indicated the correct total nine times. In the three-set sequential addition task, objects were shown to Alex and then immediately hid under a cup. This task required that he pay attention to the three sets of items presented to him, remember their quantities, add those quantities, and then verbalize the exact total. Eight out of ten times, Alex came up with the correct answer.
Unfortunately, Alex was only able to finish one round of each task before he died. Pepperberg acknowledges this shortcoming in the paper, but she points out that even with so few trials, Alex's accuracy was statistically significant. It's especially impressive given that the tasks were new to him, so his good performance cannot be explained by practice with these specific tasks. Previous experiments showed that Alex was adept at adapting and responding to novel situations, for instance by combining two words he knew to come up with a description of an object he had not seen before.
This experiment is an important footnote to Alex's legacy. The results mark Alex as one of only two non-human animals that have demonstrated the ability to represent the value of a summed set. The other animal was a chimpanzee named Sheba - and Sheba could only sum sets to a total four, compared to Alex's six.