The emergence of word order conventions: improvisation, interaction and transmission
When people improvise to convey information by using only gesture and no speech (‘silent gesture’), they show language-independent word order preferences: SOV for extensional events (e.g., boy-ball-throw), but SVO for intensional events (e.g., boy-search-ball). Real languages tend not to condition word order on this kind of semantic distinction but instead use the same order irrespective of event type. Word order therefore exemplifies a contrast between naturalness in improvisation and conventionalised regularity in linguistic systems. We present an experimental paradigm in which initially-improvised silent gesture is both used for communication and culturally transmitted through artificial generations of lab participants. In experiments 1 and 2 we investigate the respective contributions of communicative interaction and cultural transmission on natural word order behaviour. We show that both interaction and iterated learning lead to a simplification of the word order regime, and the way in which this unfolds over time is surprisingly similar under the two mechanisms. The resulting dominant word order is mostly SVO, the order of the native language of our participants. In experiment 3, we manipulate the frequency of different semantic event types, and show that this can allow SOV order, rather than SVO order, to conventionalise. Taken together, our experiments demonstrate that where pressures for naturalness and regularity are in conflict, naturalness will give way to regularity as word order becomes conventionalised through repeated usage.