The majority of multilingual research has studied monolinguals and bilinguals; however, with the increasing number of multilinguals, it is imperative to focus on multilingual language acquisition and retention. The current study compared the ability of monolinguals, bilinguals, and trilinguals to acquire and retain a morphosyntactic rule in a foreign language. Twelve monolingual, twelve bilinguals, and twelve trilingual participants completed a rule-based learning task. The participants were trained to use the preterite verb tense in Spanish, and their ability to retain this morphosyntactic rule was evaluated over three phases: baseline, immediate retention, and delayed retention. The accuracy of participants' responses and reaction time following the presentation of the stimuli was measured using E-prime software. The accuracy data found a significant main effect in the phases of learning across the participant groups. Similar results were noted for reaction time as well. There was a significant main effect of the phases of learning across the three groups for reaction time. All participants performed better during the delayed retention phase compared to immediate retention and baseline. Bilingual participants demonstrated better accuracy, while trilingual participants were the least accurate. On the contrary, trilingual participants had the shortest reaction time, while bilinguals had a longer reaction time. The current study found evidence for both facilitation and cross-linguistic interference during the process of language acquisition in multilinguals. Research in multilingual language acquisition suggests that previous language exposure may have both positive and negative impacts on novel language learning based on a range of factors
