Young children spontaneously recreate core properties of language in a new modality

Abstract

How the world's 6,000+ natural languages have arisen is mostly unknown. Yet, new sign languages have emerged recently among deaf people brought together in a community, offering insights into the dynamics of language evolution. However, documenting the emergence of these languages has mostly consisted of studying the end product; the process by which ad hoc signs are transformed into a structured communication system has not been directly observed. Here we show how young children create new communication systems that exhibit core features of natural languages in less than 30 min. In a controlled setting, we blocked the possibility of using spoken language. In order to communicate novel messages, including abstract concepts, dyads of children spontaneously created novel gestural signs. Over usage, these signs became increasingly arbitrary and conventionalized. When confronted with the need to communicate more complex meanings, children began to grammatically structure their gestures. Together with previous work, these results suggest that children have the basic skills necessary, not only to acquire a natural language, but also to spontaneously create a new one. The speed with which children create these structured systems has profound implications for theorizing about language evolution, a process which is generally thought to span across many generations, if not millennia.

Keywords: cognitive development; evolution; gesture; language.

Fig. 1.

Schematic drawing of the general setup. Children were placed in different rooms and communicated via a video channel. Candidate pictures were presented on a wooden board.

Fig. 2.

Results for experiments on creation of novel communication systems (A–F) and use of grammatical structure (G–I). (A) Dyads who spontaneously produced gestures in the first 4 trials, each of which involved a different picture. (B) Comprehension of gestures in the initiation (before role switch) and uptake phase. (C) Rate at which naive raters judged gestures from the same dyad to be more similar compared to gestures from a different dyad. (D) Rate at which raters judged later gestures to be more arbitrary. (E) Relation between ratings of arbitrariness and effort. (F) Rate of comprehension of arbitrary gestures by children who witness the form drift to arbitrary (test) and children who see only the final, arbitrary gesture (control). (G) Rate of differentiation across conditions. (H) Comprehension for gestures composed of either a single holistic gesture or a compositional gesture sequence. (I) Proportion of compositional gesture sequences by relation complexity. “Lower” refers to conditions with one modifying predicate (movement, number, and size) and “Higher” to transitive actions between 2 agents (transitive 2 and 3). In B–I, jittered transparent dots represent individual means, diamonds show group means, and vertical lines show 95% CIs. Dashed lines in B, D, and F denote performance expected by chance.