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And Baby Counts Three…

baby counts three

Infants appear to understand numbers even before they can talk. By matching voices to images, a baby shows a grasp of the abstract concept of number. Babies are showing an internal representation of ‘two-ness’ or ‘three-ness’.

In a study that could shed light on how infants first grasp the concept of number–as well as the evolutionary origins of that ability–researchers have found evidence that babies have an abstract numerical sense even before they learn to talk.

Duke University scientists Kerry Jordan and Elizabeth Brannon published their findings the week of Feb. 13-17, 2006, in the Proceedings of the National Academy of Sciences.

The research was sponsored by the National Institute of Mental Health, the National Science Foundation and the John Merck Fund.

Jordan and Brannon presented seven-month-old infants with the voices of two or three women saying, “Look.” At the same time, they showed the babies two video images: one with two women saying the word and the other with three women doing so. The researchers found that the babies spent significantly more time looking at the video image that matched the number of women talking. From that, the researchers concluded that the infants were transferring their perception of number across two different senses, sight and sound–which suggested, in turn, that babies have a truly abstract sense of numerical concepts.

In earlier work, Jordan and Brannon performed similar tests on monkeys, which also seem to exhibit numerical perception across senses.

“As a result of our experiments, we conclude that the babies are showing an internal representation of ‘two-ness’ or ‘three-ness’ that is separate from sensory modalities and, thus, reflects an abstract internal process,” said Brannon. “These results support the idea that there is a shared system between preverbal infants and nonverbal animals for representing numbers.”


Media Contacts
M. Mitchell Waldrop, NSF (703) 292-7752
Dennis Meredith, Duke University 919) 681-8054

Principal Investigators
Elizabeth M. Brannon, Duke University (919) 668-6201

Related Websites
Duke University news release:
Duke University news release on number concepts in monkeys:

What about animals and counting?

Number sense

Studying math skills in dogs to understand math in people might not be such a far-fetched idea. In fact, some research is showing that babies and animals actually have a lot in common when it comes to numbers.

Most animal math research has focused on primates. To test whether a monkey can tell the difference between numbers of objects, scientists measure how long an animal looks at things. A monkey will look longer at something that doesn’t match what it expects to see.

Using this technique, researchers have shown that monkeys can add and subtract small numbers of objects. If they are shown one apple slice and then another, for example, they know there should be a total of two. They will then look for a longer time at a pile of three or one than at a pile of two.

TamarinRecent evidence also shows that some primates know the difference between more and less. Cotton-top tamarins look longer at two Froot Loops than at one. Rhesus macaques look longer at three turnips than at two.

Likewise, 12-month-old babies look longer at a bigger pile of sugar cookies. Even though they can’t talk or count, the babies seem to know how to go for more.

Most interesting of all, says cognitive scientist Claudia Uller, is that those skills fall apart at about the same number in both monkeys and babies.

“It’s so incredible,” says Uller, who is at the University of Louisiana at Lafayette. “It breaks down at around four. If you give babies two or three, they’ll go for three. At three versus four, their choices are random. At four versus six, they’re random.” The same is true for monkeys and tamarins.

Because primates and people are so closely related, Uller wanted to try the same experiment with a completely different kind of animal: salamanders. Amazingly, she found the same results.

When shown test tubes holding different numbers of live fruit flies, red-backed salamanders looked at the tube that held more. But only up to a certain point. Just as in babies and monkeys, the system seemed to break down around four. Uller published her results recently in the journal Animal Cognition.

Her study is the first example that an animal other than a primate might be able to distinguish between more and less. Another scientist is now looking for the same phenomenon in fruit flies, Uller says. Further research could help explain the biology behind basic math skills.

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How high can animals count?

Additional tests by Hauser and other researchers reveal that monkeys can count up to four. The human ability to count to higher numbers apparently came only after we evolved language and developed words to describe quantities like 25 and 1,000.

Some human cultures still don’t use large numbers. The Hadza people, hunter-gatherers in Tanzania, for example, have words only for “one,” “two,” and “three”; anything more is “many.” They are aware that a picture with 30 dots displays a larger number than one with 20 dots (as are monkeys), but they have no words for the precise numbers of dots.

The bottleneck between human and nonhuman thinking involves not just words, but the ability to recombine words in an endless variety of new meanings. That appears to be a unique human capability. Chimpanzees have a rich social and conceptual life, Hauser maintains, but they can’t discuss it with each other.

The next step in determining how much thinking ability humans share with other animals will involve scanning the brains of both while they do the same cognitive tasks. Harvard psychologists have already begun to do this in a collaboration with researchers from the University of Massachusetts Medical School in Worcester and the Max Planck Institute in Germany. Monkeys may exhibit the same kind of intellectual behavior as humans, but do they both use the same areas of the brain?

“We have a great deal of data that show what areas of the brain are activated when humans respond to various situations,” Hauser points out. “Now we will determine if monkeys and other animals utilize the same brain circuits.”

So far, the monkeys are adapting well to experiments at the University of Massachusetts. They move into harnesses in brain scanning instruments, such as MRI machines, without difficulty. Measurements of their stress levels show that after five days of training, marmoset monkeys feel as comfortable as they do in their home cages with their own social group.

For some people, such research will not provide a satisfactory answer to the question: Do animals really think? These people define thinking as having a sense of self, beliefs that go beyond raw perceptions, emotions such as empathy, and the ability to imagine a situation remote in time and place and predict an outcome.

“Those capabilities cannot be illuminated by brain scanning,” Hauser admits. “But experiments using other techniques are beginning to shed light on what kinds of perceptual and computation skills animals bring to analyzing the world, and in what ways these skills are different from our own.”

I think, therefore I am. – Descartes

For more information about nonhuman thinking, see Hauser’s book “Wild Minds,” (Henry Holt, 2000). Hauser will debate distinguished linguist Noam Chomsky on March 30 at Harvard at a conference sponsored by the Language Evolution Society.

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