Brazil's Piraha grasp numbers without words: study challenges theories linking language, thought

Science News, July 19, 2008 by Bruce Bower

One is the loneliest number that you'll ever do, especially if you don't even have a word for it. That's the situation of the Piraha people, denizens of Brazil's Amazon rainforest who have no term for the number one or for any other exact quantity, a new study finds.

Until now, researchers have not demonstrated the absence of a way to express the number one in any language, according to a team led by Massachusetts Institute of Technology cognitive scientist Edward Gibson.

Yet Piraha individuals can still identify the number of items that an experimenter places in front of them, Gibson's team reports. The new findings challenge the long-standing idea that number words enable people to think about and recognize exact quantities of items.

"These results suggest that number words do not change our underlying representations of number, but instead are a cognitive technology for keeping track of the exact size of large sets over time and in different contexts," says coauthor Michael Frank of MIT. The new study was published online and will appear in an upcoming Cognition.

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The team first examined whether the Piraha employ counting words, as was described in a 2004 study conducted by psycholinguist Peter Gordon of Columbia University. Gordon concluded that the Brazilian tribe has words for one, two and many (SN:12/10/05, p. 376). However, Daniel Everett of Illinois State University in Normal, a longtime Piraha researcher and coauthor on the new study, initially questioned Gordon's results.

The new study explores Everett's contention that no words for exact numbers exist in the Piraha language. For each of six adult Piraha volunteers, a researcher placed one wooden thread spool on a table and added spools one at a time until reaching 10 spools. For each quantity, the experimenter used the Piraha language to ask volunteers "How much is this?" Four of the same volunteers then performed this exercise as the researcher removed one spool at a time from a set of 10 spools until one remained.

Participants used the same three words for dramatically different ranges of quantities when dealing with increasing or decreasing numbers of spools. For increasing quantities, these words roughly corresponded to one, two and many. For decreasing quantities, these three words were used to denote from one to six spools, from four to 10 spools and from seven to 10 spools.

These results indicate that the three Piraha words refer to general quantities, such as few, some and more, Frank says. Many other foraging groups, as well as the Piraha in Gordon's study, have been reported to have words for one, two and many based only on responses to increasing numbers of items. Some of those groups may, like the Piraha, reveal an absence of number words when responses to decreasing quantities are considered, Frank proposes.

In a second experiment, 14 Piraha adults reproduced exact quantities of objects despite lacking number words. Participants facing a line of one to 10 spools almost always chose the same number of uninflated balloons to put in a matching line. Still, the same individuals often muffed tasks that required them to track and remember precise amounts, such as choosing a matching number of balloons after watching an experimenter drop spools one at a time into a can.

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Number words are cultural inventions that greatly enhance the ability to monitor the exact sizes of large groups of objects, the researchers propose. Speakers of languages with number words thus find it easy to recall and re-create the number of spools dropped into a can.

To some extent, this idea challenges the nearly 70-year-old argument of Edward Sapir and Benjamin Whorf, both Yale University anthropologists. They proposed that the structure of a language conditions the ways its speakers think about the world. Thus, speakers of different languages view critical aspects of the world in different ways. The Sapir-Whorf hypothesis has attracted much criticism, especially over the last 15 years, from researchers who regard the mind as a collection of evolved thinking devices that operate independently of language.

Scientific opinions vary widely on what the new study shows about numerical thinking among the Piraha. Gibson's team makes a good case for the absence of Piraha words that represent exact quantities, including a word for one, remarks psychologist David Barner of the University of California, San Diego.

Barner's own studies indicate that English-speaking children don't immediately realize that singular nouns, such as a banana, represent the numerical equivalent of one banana. At 2 years of age, youngsters understand that one refers to single items but assume that a means at least one, he says. As they learn about terms such as some and all, children gradually adopt a as a stand-in for one, Barner suggests.

Harvard University psychologist Elizabeth Spelke agrees that the Piraha lack number words but questions whether they exhibit an underlying knowledge of precise amounts as proposed by Gibson's team. "The prize question, whether exact number concepts such as seven depend on number words and verbal counting, is still open," Spelke says.