Structural biases that children bring to language learning: A cross-cultural look at gestural input to homesign

Abstract

Linguistic input has an immediate effect on child language, making it difficult to discern whatever biases children may bring to language-learning. To discover these biases, we turn to deaf children who cannot acquire spoken language and are not exposed to sign language. These children nevertheless produce gestures, called homesigns, which have structural properties found in natural language. We ask whether these properties can be traced to gestures produced by hearing speakers in Nicaragua, a gesture-rich culture, and in the USA, a culture where speakers rarely gesture without speech. We studied 7 homesigning children and hearing family members in Nicaragua, and 4 in the USA. As expected, family members produced more gestures without speech, and longer gesture strings, in Nicaragua than in the USA. However, in both cultures, homesigners displayed more structural complexity than family members, and there was no correlation between individual homesigners and family members with respect to structural complexity. The findings replicate previous work showing that the gestures hearing speakers produce do not offer a model for the structural aspects of homesign, thus suggesting that children bring biases to construct, or learn, these properties to language-learning. The study also goes beyond the current literature in three ways. First, it extends homesign findings to Nicaragua, where homesigners received a richer gestural model than USA homesigners. Moreover, the relatively large numbers of gestures in Nicaragua made it possible to take advantage of more sophisticated statistical techniques than were used in the original homesign studies. Second, the study extends the discovery of complex noun phrases to Nicaraguan homesign. The almost complete absence of complex noun phrases in the hearing family members of both cultures provides the most convincing evidence to date that homesigners, and not their hearing family members, are the ones who introduce structural properties into homesign. Finally, by extending the homesign phenomenon to Nicaragua, the study offers insight into the gestural precursors of an emerging sign language. The findings shed light on the types of structures that an individual can introduce into communication before that communication is shared within a community of users, and thus sheds light on the roots of linguistic structure.

Keywords: Co-speech gesture; Complex noun phrases; Complex sentences; Homesign; Linguistic input; Nicaraguan Sign Language.

Figure 1.

A Nicaraguan hearing mother and her deaf homesigning child each producing DRINK, a gestural emblem used by hearing speakers in Nicaragua.

Figure 2.

Mean number of child-directed communicative acts produced by hearing family members in Nicaragua vs. USA, classified according to whether the act contained gesture-alone, speech + gesture, or speech-alone. Error bars indicate standard errors.

Figure 3.

A Nicaraguan homesigner producing a complex sentence (A) and a homesigner producing a complex noun phrase (B).

Figure 4.

Scatter plots of gesture string length (top), complex gesture sentences (middle), and complex gesture noun phrases (bottom) for hearing family members (left graphs) and homesigning children (right graphs) as a function of culture (Nicaragua in blue, USA in red). Note that two datapoints partially obscure each other for the USA participants, at ages 3;11 and 4;0, in the length of gesture string graph; and one datapoint for the Nicaraguan participants, at age 3;9, in the noun phrase graph is partially obscured by the datapoints for the USA participants.

Figure 5.

Top: Bar graphs contrast gesture string length, complex sentences, and complex noun phrases for homesigners (red) vs. hearing family members (blue) in Nicaragua (left bars in each graph) and the USA (right bars). Error bars indicate standard errors. Bottom: Scatterplots of the same measures showing the relation between individual homesigners (x-axis) and their hearing family members (y-axis) in Nicaragua (black triangles) and the USA (white dots).