Implicit learning across the lifespan: NZ migrants build a Māori proto-lexicon, NZ expats retain one

Regular incidental exposure to a language that someone does not speak can allow a person to build a proto-lexicon of the language – a set of implicitly stored word forms without semantic knowledge. Previous research shows that non-speakers of Māori in New Zealand (NZ) have well-developed phonotactic and proto-lexical knowledge of Māori. However, we still do not know whether exposure in early childhood is completely necessary for the formation of the proto-lexicon, nor how much proto-lexical knowledge develops from exposure in childhood versus exposure in adulthood. It is also unclear how robust these implicit memories are. To address these gaps, we examine the extent to which childhood exposure and/or ongoing consistent adult exposure are necessary conditions for the creation and/or maintenance of a proto-lexicon by comparing four groups (expats, migrants, local adolescents and local adults). The results reveal that migrants’ proto-lexicon is greater than that of local adolescents, indicating that early childhood exposure to the language is not necessary. In addition, expats retained robust memory for their proto-lexical knowledge, acquired before moving overseas. Thus, implicit learning in adulthood plays a significant role and a proto-lexicon can be built and maintained over the course of the entire lifespan.