This study investigates the neurocognitive underpinnings of early language learning in adults and examines the modulating effects of individual differences in prior bilingual experience and cognitive capabilities. This study used a pre/post short-term longitudinal design with a 10-day Dutch language training via Rosetta Stone. Event-Related Potentials (ERPs) were used to track neurophysiological changes during a Semantic Categorization Task (SCT), which was designed to measure the lexicalization of new words. Results showed significant reductions in N400 amplitude at post-test across all words, indicating successful semantic integration as shown in McLaughlin et al., (2004) and Bakker et al., (2015) and rapid neural adaptation (after only 5-7 hours of learning). Higher bilingual experience predicted more reduced N400 amplitudes for cognate words, suggesting bilingualism may aid in the lexicalization of similar words across languages. Additionally, better inhibitory control (IC) predicted smaller N400s for cognates but larger N400s for non-cognates--suggesting that individuals with higher inhibitory control may manage cross-linguistic interference better for cognates, but may incur a processing cost for non-cognates. This work highlights the importance of individual differences in early language learning and advances our understanding of the interplay between language experience and neuroadaptation (Pliatsikas, 2020). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]