Examining the Paradox of Adult Second Language Word and Grammar Learning
Abstract
Background: Adults generally demonstrate advanced cognitive skills compared to children, with second language (L2) learning being a key exception, particularly within the grammar domain. As optimal vocabulary and grammar learning are believed to engage in distinct explicit and implicit learning mechanisms, respectively, the advanced neurocognitive mechanisms underpinning adults’ higher-order cognitive skills may particularly interfere with implicit grammar learning. The objective of this dissertation was to examine select neural and cognitive factors that may contribute to word and grammar learning differences.
In Study 1, I investigated the neural correlates of artificial vocabulary and morphology learning using functional Near-Infrared Spectroscopy (fNIRS). Despite adults outperforming in explicit vocabulary outcomes compared to implicit grammar generalization, cortical differences between processing the two language components were minimal. On the other hand, significant changes in neural activity were observed in all four cortical lobes over the course of the initial language learning period, demonstrating the widespread cortical engagement inherent in the process of L2 learning.
In Study 2, I examined the impact of effortful learning on implicit word and grammar learning outcomes using a modified statistical language learning paradigm with an underlying grammatical pattern. Performance on speeded syllable detection tasks using familiar and unfamiliar targets revealed that effortful and passive learning conditions resulted in comparable implicit learning outcomes related to word segmentation and grammar generalization. Thus, directing effort towards learning neither facilitated nor interfered with implicit L2 attainment.
In Study 3, I investigated whether individual differences in statistical learning of words and/or grammatical patterns were related to domain-general cognitive abilities. The findings indicate that performance on tasks evaluating short-term memory, attention, strategic thinking, reasoning, and planning skills were not related to implicit word or grammar learning outcomes.
Conclusion: Together, this dissertation presents empirical evidence that adults learn vocabulary more easily than grammatical patterns, but learning success is not related to domain-general cognitive mechanisms, at least concerning implicit representations of language. These findings are discussed in relation to existing literature and emerging theories of L2 learning. This research has important methodological implications and provides valuable insights to inform pedagogical practices for foreign language instruction.