The Pirahã Controversy: Numbers (part 3)

Apr 8, 2012 by

In the previous post, I discussed a study conducted by Dr Peter Gordon that appears to show that the Pirahã not only lack number words (as has been argued previously by Dan Everett), but also lack the necessary cognitive mechanisms that would allow them to appreciate numerosities beyond two or three. According to Gordon, “numerical cognition is clearly affected by the lack of a counting system in the language”. But is this necessarily so?

A more recent study conducted by a team of researchers led by MIT professor of brain and cognitive sciences Edward Gibson and including Michael Frank, a graduate student in Gibson’s lab; Evelina Fedorenko, a postdoctoral associate at the McGovern Institute for Brain Research at MIT, and Dan Everett, challenged Gordon’s conclusions. They’ve found that the Pirahã succeeded in simple one-to-one matching task, suggesting that the concept of exact quantity (the idea that adding or  subtracting one object makes a difference) does not depend on linguistic knowledge. Moreover, this team has succeded in turning English speakers into Pirahã speakers by not letting them use verbal counting. In order to do so, they used the verbal shadowing technique: the English-speaking experimental subjects had to repeat meaningful speech immediately after hearing it while performing the experimental task. By doing so, the researchers were able to show that memory for exact quantities, but not one-to-one matching, is dependent on language.

The experiment was set up in the following way: twenty participants from MIT and the surrounding community, ranging in age from 18 to 50, had to perform five matching tasks like the ones on Gordon’s experiment with the Pirahã. The tasks required the participants to observe some quantity of thread spools and to put out a line of un-inflated balloons exactly matching the quantity of spools that they saw, which varied from 4 to 12. The task were:

  • a one-to-one matching task: the spools evenly placed from the participant’s left to their right
  • an uneven matching task: the spools were broken into smaller groups of one to four
  • an orthogonal matching task: the line of spools ran from close to the participant to further away, rather than from left to right
  • a hidden matching task: the line was hidden by the experimenter after the spools were placed by placing a manila folder in front of the spools
  • a nuts-in-a-can task: the experimenter placed spools one by one into an opaque cup

On each trial, the experimenter would begin by starting the audio which the participant listened to over headphones. The participants had to repeat the text that they heard while performing the matching tasks.

It was found that for the English speakers, as for the Piraha, the one-to-one and uneven matching tasks were easiest, followed by the orthogonal and hidden matching tasks, while the nuts-in-a-can task was by far the hardest. While performance in one-to-one matching tasks was largely preserved without the use of number language, which was blocked by the verbal shadowing task, performance on more memory intensive tasks was dramatically impaired. Thus, occupying the verbal resources of speakers of a language with numbers produced a pattern of data remarkably similar to the data of speakers of a language without numbers.

Gibson and his team concluded that all human beings share a variety of core numerical capacities (which is probably shared with many other species as well). But both learning and using the ability to remember exact quantities larger than three or four appears to depend crucially on verbal mechanisms. Thus, languages which contain recursive count lists allow their speakers to transcend the core numerical capacities.

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Frank, M. C., Everett, D. L., Fedorenko, E., & Gibson, E. (2008). Number as a cognitive technology: Evidence from Pirahã language and cognition. Cognition 108(3): 819-824.

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