Systematicity, but not compositionality: Examining the emergence of linguistic structure in children and adults using iterated learning

Abstract

Recent work suggests that cultural transmission can lead to the emergence of linguistic structure as speakers' weak individual biases become amplified through iterated learning. However, to date no published study has demonstrated a similar emergence of linguistic structure in children. The lack of evidence from child learners constitutes a problematic gap in the literature: if such learning biases impact the emergence of linguistic structure, they should also be found in children, who are the primary learners in real-life language transmission. However, children may differ from adults in their biases given age-related differences in general cognitive skills. Moreover, adults' performance on iterated learning tasks may reflect existing (and explicit) linguistic biases, partially undermining the generality of the results. Examining children's performance can also help evaluate contrasting predictions about their role in emerging languages: do children play a larger or smaller role than adults in the creation of structure? Here, we report a series of four iterated artificial language learning studies (based on Kirby, Cornish & Smith, 2008) with both children and adults, using a novel child-friendly paradigm. Our results show that linguistic structure does not emerge more readily in children compared to adults, and that adults are overall better in both language learning and in creating linguistic structure. When languages could become underspecified (by allowing homonyms), children and adults were similar in developing consistent mappings between meanings and signals in the form of structured ambiguities. However, when homonimity was not allowed, only adults created compositional structure. This study is a first step in using iterated language learning paradigms to explore child-adult differences. It provides the first demonstration that cultural transmission has a different effect on the languages produced by children and adults: While children were able to develop systematicity, their languages did not show compositionality. We focus on the relation between learning and structure creation as a possible explanation for our findings and discuss implications for children's role in the emergence of linguistic structure.

Adults are more efficient in creating and transmitting novel signalling systems than children

“…Our findings are in line with the study by Raviv & Arnon (2018), where learnability of meaningful signals was also higher in adults than 6 -12-year-old children. Moreover, as in the present study, compositional structure did not exceed chance levels in that study either although it was significantly higher in adults.…”

“…Moreover, as in the present study, compositional structure did not exceed chance levels in that study either although it was significantly higher in adults. There are at least two possible reasons for why structure and iconicity did not emerge reliably in these experiments: First, both in Raviv and Arnon (2018) and in the present Language transmission in adults and children 18 study, the training phase was considerably shorter than in many previous iterated learning studies, a methodological constraint that was necessary to sustain children's attention on the task. A shorter training phase may have simply not provided enough opportunity to explore the iconic and structural potential of the signalling domains.…”

“…The results showed that compositional structure Language transmission in adults and children 7 emerged only in the adults but not in the children. Secondly, Raviv and Arnon (2018) trained 6-12-year-old children and adults to orally reproduce bisyllabic pseudo-words presented as signals for twelve meanings that varied on three dimensions. To encourage productivity, participants were trained on only nine out of the twelve signal-meaning pairs, and subsequently tested on the entire set.…”

Playing with language, creating complexity: Has play contributed to the evolution of complex language?

“…However, children's innovative potential is more apparent in the acquisition of instrumental skills rather than social conventions . Because language is a social convention, and children are faithful imitators of social conventions, it is doubtful that children are the primary agents of linguistic innovation and language change …”

“…97 Because language is a social convention, and children are faithful imitators of social conventions, 97 it is doubtful that children are the primary agents of linguistic innovation and language change. [98][99][100] Instead, we argue that a propensity for playful innovation that has been cemented with respect to tools and objects during childhood reaches into adolescence and adulthood, where it may provide one engine for linguistic innovation and change that has allowed language to accommodate the complex social conditions made possible by self-domestication. As argued earlier, to extend playing behavior into adulthood is one of the hallmarks of domestication.…”