Abstract
Language learning occurs in distinct phases. Whereas some improvement is evident during training, offline memory consolidation processes that take place after the end of training play an important role in learning of linguistic information. The timing of offline consolidation is thought to depend on the type of task, with generalization of implicit knowledge suggested to take more time and sleep to consolidate. The current study aims to investigate individual differences in the timing of consolidation following learning of morphological inflections in a novel language in typical adults. Participants learned to make plural inflections in an artificial language, where inflection was based on morpho-phonological regularities. Participants were trained in the evening, and consolidation was measured after two intervals: 12 h (one night) and 36 h (two nights) post training. We measured both inflection of trained items, which may rely on item-specific learning, and generalization to new untrained items, which requires extraction of morpho-phonological regularities. The results for both trained and un-trained items showed two patterns of consolidation: early versus late, that is while some participants improved during the first night, others, who deteriorated in performance during the first night, improved in the later consolidation interval. Importantly, phonological awareness in L1 predicted early consolidation for trained items. Furthermore, there was no association between participants’ consolidation trajectory in trained and untrained items. Our results suggest that consolidation timing depends on the interaction between task characteristics and individual abilities. Moreover, the results show that prior meta-linguistic knowledge predicts the quality of early consolidation processes. These results are consistent with studies in rodents and humans, showing that prior knowledge accelerates consolidation of newly learnt episodic memory. Finally, the rate of consolidation across exposures to the language might explain some of the variability found in the attained level of second language proficiency.
Highlights
Learning a second language is a difficult and prolonged endeavor, with large variability in learning rate, trajectory and gained proficiency (Roberts, 2012; Dornyei, 2014)
By examining the consolidation of novel words and their morphological inflections in a healthy adult population on two consecutive days, the current study identified individual variability in the timing of consolidation, with early and late offline improvers
This variability was identified both in a task that relies on implicit extraction of statistical regularities, and in a task that involves item-specific learning
Summary
Learning a second language is a difficult and prolonged endeavor, with large variability in learning rate, trajectory and gained proficiency (Roberts, 2012; Dornyei, 2014). Whereas some improvement occurs on-line, during exposure and training, there is evidence for consolidation processes, which manifest as off-line gains after. Consolidation of Second Language Learning the end of training (Rasch and Born, 2013; James et al, 2017). Most previous research has focused on individual differences in online language learning, and less is known about possible individual differences in consolidation of novel linguistic information. The current study addresses this issue in the context of an artificial language learning task, of novel morphological inflections, previously shown to rely on fronto-striatal mechanisms (Nevat et al, 2017). We examined individual differences in consolidation of trained items and untrained items which involves the ability to extract regularities from the input, and their possible links to individual differences in meta-linguistic abilities
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