Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Doctor of Philosophy




Joanisse, Marc F.


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.

Summary for Lay Audience

Compared to children, adults typically demonstrate advanced cognitive skills. Yet, the older we get, the more difficult it is to learn a new language. This is especially true for learning new grammatical patterns, whereas we can learn new vocabulary words more easily. Some research suggests that learning new words and grammatical patterns rely on different brain regions and learning mechanisms that compete with one another. Specifically, adults advanced cognitive skills may be beneficial for learning new words but may interfere with learning new grammatical patterns. I aimed to address this theory using three research studies that examined neural and cognitive differences between word and grammar learning. In the first study, I used a neuroimaging tool to look at the cortical (outer brain) regions that are involved in learning a new language. The findings demonstrated that adults learned new words more easily than grammatical patterns, but there were only minimal differences in the brain activity between vocabulary and grammar processing. On the other hand, regions all over the cortex were found to be involved in the early stages of learning, suggesting that language learning involves a wide range of cognitive processes. In the second study, I tested whether applying effort towards learning a new language helps or interferes with language learning outcomes. The results revealed that putting extra effort into learning did not make a significant difference in either word or grammar learning success. In the third study, I explored the relationships between language learning and a variety of cognitive skills such as memory and attention. The results indicated that performance on cognitive tests were not related to how well individuals learned words or grammatical patterns. Together, these studies provide scientific evidence that adults have difficulty with learning grammatical patterns more than new vocabulary words, but this difficulty may not be related to other cognitive skills or how hard we try to learn. I discuss these findings in relation to emerging theories and highlight the important implications that come from this work in terms of improving scientific methodology and foreign language instruction.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License