Innovation of word order harmony across development

The tendency for languages to use harmonic word order patterns–orders that place heads in a consistent position with respect to modifiers or other dependents–has been noted since the 1960s. As with many other statistical typological tendencies, there has been debate regarding whether harmony reflects properties of human cognition or forces external to it. Recent research using laboratory language learning has shown that children and adults find harmonic patterns easier to learn than non-harmonic patterns (Culbertson, Smolensky, & Legendre, 2012; Culbertson &Newport 2015). This supports a link between learning and typological frequency: if harmonic patterns are easier to learn while non-harmonic patterns are more likely to be targets of change,then, all things equal, harmonic patterns will be more frequent in the world’s languages. However,these previous studies relied on variation in the input as a mechanism for change in the lab; learners were exposed to variable word order, allowing them to shift the frequencies of different orders sothat harmonic patterns became more frequent. Here we teach adult and child learners languages that are consistently non-harmonic, with no variation. While adults perfectly maintain these consistently non-harmonic patterns, young child learners innovate novel orders, changing non-harmonic patterns into harmonic ones