Their hearing losses prevent them from acquiring Spanish
and they do not have access to Nicaraguan Sign Language.
Homesigners in Nicaragua are famous among linguists for spontaneously creating a fully formed language when they were first brought together at a school for the deaf in the 1970s. But many homesigners stay at home, where they share a language with no one. Their “home signs” are completely made up, and lack consistent grammar and specific number words.
Over the course of three month-long trips to Nicaragua in 2006, 2007 and 2009, Spaepen gave four adult Nicaraguan homesigners a series of tests to see how they handled large numbers. They later gave the same tasks to control groups of hearing Nicaraguans who had never been to school and deaf users of American Sign Language (which does use grammar and number words) to make sure the results were not just due to illiteracy or deafness.
The four homesigners show no congenital cogni- tive deficits and performed as well as hearing siblings and friends on tasks testing mental rotation skills. They hold jobs, make money, and interact socially with hearing friends and family.
We first asked whether homesigners were familiar enough with their society’s moneyed economy to make correct judgments about monetary values. We designed a series of tasks to assess their recognition of currency (shown, for example, by gesturing a five and two zeroes for a 500-unit bill); their ability to compare the relative value of the currency (shown, for example, by determining whether a 10-unit or a 20-unit bill has more value); and their ability to compare coins and bills of different currency type (shown, for example, by determining whether a set of nine 10-unit coins has more or less value than a 100-unit bill). All four homesigners identified money correctly and could assess its relative value, and three of the four homesigners performed with greater than chance accuracy on all monetary tasks.
Homesigners were 100% accurate on target sets of one, two, and three for both time-unlimited (Fig. 2A) and time-limited (Fig. 2B) versions of the task.† However, they performed significantly less well on target sets greater than three on both versions, coming close to the value of the target number but achieving the exactly correct value on fewer than half the trials.
In the second version of the “which is more” task, participants saw 40 trials, each of which contained two sets of coins or bills. In this task, the coins on each side of the comparison were all of one kind, but homesigners had to compare across types of coins or bills. There were four types of trials, ranging in difficulty, as follows:
Type I, which included four trials, showed small numbers of bills or coins of the same denomination. These were controls to make sure homesigners were on task (e.g., two C$5 coins vs. three
Type II, which included 12 trials, showed small numbers of bills or coins of different denominations (e.g., three C$20 bills vs. one C$50 bill, two C$5 coins vs. three C$10 bills).
Type III, which included 12 trials, showed large numbers of bills or coins of different denominations with a small monetary difference between sides (e.g., six C$5 coins vs. two C$20 bills, seven C$10 bills vs. four C$20 bills).
Type IV, which included 12 trials, showed large numbers of bills or coins of different denominations with a large monetary difference between sides, always at a 1:2 or 2:3 ratio (e.g., 10 C$10 bills vs. two C$100 bills, 12 C$5 bills vs. three C$10 bills).
Trials of different types were interspersed in a quasi-random fixed order. Side of the winner, the larger number of coins being the winner, and the larger denomination being the winner were all counterbalanced across trials within each type. Moreover, within each type, homesigners saw four trials that compared coins to coins, four trials that compared bills to coins, and four trials that compared bills to bills.
Fig. 1 indicates the homesigners’ and the unschooled hearing controls’ performance on this task. Both groups did quite well. The hearing controls were far above chance on all trial types (one-sample t tests: all P < 0.01). The homesigners were above or marginally above chance on all trial types except type III [one-
sample t tests: type I, t(3) = 7.00, P < 0.01; type II, t(3) = 3.323, P < 0.05; type III, t(3) = 2.211, P = 0.114; type IV, t(3) = 2.920, P = 0.06].
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