Number without a language model

Elizabet Spaepen; Marie Coppola; Elizabeth S. Spelke; Susan E. Carey; Susan Goldin-Meadow

doi:10.1073/pnas.1015975108

New Research In

Contributed by Susan E. Carey, December 7, 2010 (sent for review June 28, 2009)

Abstract

Cross-cultural studies suggest that access to a conventional language containing words that can be used for counting is essential to develop representations of large exact numbers. However, cultures that lack a conventional counting system typically differ from cultures that have such systems, not only in language but also in many other ways. As a result, it is difficult to isolate the effects of language on the development of number representations. Here we examine the numerical abilities of individuals who lack conventional language for number (deaf individuals who do not have access to a usable model for language, spoken or signed) but who live in a numerate culture (Nicaragua) and thus have access to other aspects of culture that might foster the development of number. These deaf individuals develop their own gestures, called homesigns, to communicate. We show that homesigners use gestures to communicate about number. However, they do not consistently extend the correct number of fingers when communicating about sets greater than three, nor do they always correctly match the number of items in one set to a target set when that target set is greater than three. Thus, even when integrated into a numerate society, individuals who lack input from a conventional language do not spontaneously develop representations of large exact numerosities.

Footnotes

¹To whom correspondence may be addressed. E-mail: liesje{at}uchicago.edu or scarey{at}wjh.harvard.edu.
Author contributions: E.S., M.C., E.S.S., S.E.C., and S.G.-M. designed research; E.S. and M.C. performed research; E.S. analyzed data; and E.S., M.C., E.S.S., S.E.C., and S.G.-M. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1015975108/-/DCSupplemental.
*Some have suggested that the Pirahã have words for “one” and “two” (2); however, other work suggests that the meanings of these words are not exact, but approximate (3).
^†In fact, homesigners were 100% accurate on both versions of the card task for sets of four, a number that is within the subitizable range for adults and, on those grounds, could be classified as a small (rather than a large) number. We categorized four as a large number to facilitate comparison with data from the Pirahã (2). Moreover, removing four from the large number category in the homesigners’ data would further depress their success rates for large numbers, which would serve only to strengthen the patterns we report.
^‡In addition to overall performance, evidence that the homesigners did not view the time-unlimited task as a request for approximate values comes from their spikes of accuracy at targets of 15 and 20 in the time-limited condition (which clearly required estimation), but not in the time-unlimited condition in which homesigners were no more accurate on 15 and 20 than on 14, 16, or 19. When estimating in the time-limited condition, participants often “round”—in this case to the values given by whole hand gestures—but in the time-unlimited condition, they seemed to be attempting exact responses.