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Researchers explore whether parrot has concept of zero

A bird may have hit on a concept that eluded mathematicians for centuries—possibly during a temper tantrum.

Alex, a Grey parrot (Psittacus erithacus). (Courtesy Jenny Pegg)

Oddly, it seems he may have achieved the feat during a temper tantrum, the scientists say.

Although zero is an obvious notion to most of us, it wasn’t to people long ago. Scholars say it came into widespread use in the West only in the 1600s; India had it about a millennium earlier.

Yet Alex, a 28-year-old Grey parrot, recently began—unprompted—using the word “none” to describe an absence of quantity, according to researchers at Brandeis University in Waltham, Mass.

Alex thus possesses a “zero-like concept,” wrote the scientists.

Years earlier, Alex had been taught another meaning of “none,” as a lack of information, they added. But his feat was to extend the concept to a context involving numbers, during a test of his counting skills. 

The researchers, Irene Pepperberg and Jesse Gordon, described the findings in the May issue of The Journal of Comparative Psychology, a research journal.

Alex’s apparent insight into nothingness doesn’t necessarily extend to other arithmetical talents, the researchers noted: the researchers found these to lag in some respects behind those of young human children.

The scientists also said it will take further study to determine whether Alex—who has been the subject of intelligence and communication tests throughout his life—really understands zero. 

Zero and none “are not identical,” Pepperberg wrote in a recent email. But since Alex never learned “zero,” the researchers said, it’s impressive that he started using a word he knew to denote something like it: an absence of a quantity.

Also unclear, though, was whether by “none” he meant no colors, no objects or something else. 

“We just started yet another series of experiments to see if he can easily be trained to understand that ‘none’ can be used for true zero,” Pepperberg said via email. It looks like he can, she added, but it’s “far too early to make serious claims.”

Chimps and possibly squirrel monkeys show some understanding of zero, but only after training, the researchers said. So Alex’s feat is the first time this has been documented in a bird, “and the first time it occurred spontaneously,” Pepperberg said via email.

But the achievement didn’t come without a few bumps.

The story began when researchers started testing Alex to see whether he understood small numbers, between one and six. Zero wasn’t expected of him. The researchers would lay out an array of objects of different colors and sizes, and asked questions such as “what color four?”— meaning which color are the objects of which there are four.

Alex performed well on this, with no training, for dozens of trials, the researchers recounted. But then he balked. Alex started ignoring questions, or giving wrong answers, seemingly deliberately. He seemed to enjoy the experimenters’ frustrated reactions, they said. 

There was evidence, they added, that his stubbornness stemmed from boredom with the rewards he had been getting for right answers. The researchers found some more interesting toys to give as rewards. After two weeks of obstructionism, Alex grudgingly returned to the game, though he occasionally seemed to lapse back.

One of these apparent lapses occurred one day when an experimenter asked Alex “what color three?” Laid out before Alex were sets of two, three and six objects, each set differently colored. 

Alex insisted on responding: “five.” This made no sense given that the answer was supposed to be a color.

After several tries the experimenter gave up and said: “OK, Alex, tell me: what color five?”

“None,” the bird replied. This was correct, in that there was no color that graced exactly five of the objects. The researchers went on to incorporate “none” into future trials, and Alex consistently used the word correctly, they said.

“We cannot determine what cognitive process led to this behavior,” the researchers wrote. “We suggest only that his action, occurring soon after a period of noncompliance, resulted from a lack of interest in the given task and was a possible attempt to make the procedure more challenging.”

In the future, the researchers said they want to test Alex for his ability to add and subtract small quantities, including possibly zero. 

As they investigate whether Alex really understands zero, they will also have to untangle the meanings of “none” and “zero.”

Merriam-Webster’s online dictionary defines zero as follows: “the arithmetical symbol… denoting the absence of all magnitude or quantity,” or “the number between the set of all negative numbers and the set of all positive numbers.” The entry continues with several more definitions. 

By contrast, the dictionary defines “none” as not any, not one, nobody, not any such thing or person, no part, or nothing.

Of course, these words may well mean different things to the authors of a dictionary, and to a parrot.

A related question is the history of both words. “None” seems to be older than “zero.” 

Zero was common in the West only from the 1600s on, though similar concepts appeared earlier in fits and starts, according to J.J. O’Connor of the University of St. Andrews in St. Andrews, Scotland. 

In pre-zero times, O’Connor wrote in an online essay, some mathematicians tied themselves in knots to solve problems that would have been much easier with a zero. But ancient peoples as a whole probably didn’t think of it because they didn’t need it: “If ancient peoples solved a problem about how many horses a farmer needed,” he wrote, “then the problem was not going to have 0 or –23 as an answer.”

“None” is considerably older than “zero” in Western cultures. It’s related to a neinn—an early medieval Viking word—and is similar to the still older Latin word noenum, meaning “not one,” according to the Online Etymology Dictionary.

Whatever the etymological roots of Alex’s utterances, his performance has its limitations, the researchers said. Several years ago, they tried to teach him to recite a number line by presenting written numerals on their own, without reference to groups of items. Alex performed rather poorly. Schoolchildren, by contrast, can usually learn this fairly easily.

Thus Alex’s apparent insight into zero doesn’t necessarily reflect across-the-board mathematical brilliance. Alex’s abilities might parallel those of children “who have trouble learning language and counting skills,” the researchers wrote.

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