Research

Overview

Language is an incredibly complex phenomenon that most humans master in the earliest years of life. So, why is language learning post-childhood such a difficult task? What intrinsic differences underlie post-adolescent language learning at the cognitive level? What neurobiological differences influence this process? Why is there such variability in outcomes for language learning in adults? Do bilinguals rely on similar mechanisms for both languages?

My research attempts to answer these questions by exploring the factors that underlie language acquisition and multilingualism. I accomplish this by investigating language processing in healthy individuals and individuals with aphasia, a severe communication disorder that typically follows a stroke. More specifically, I examine morphosyntax, an aspect of language that is particularly difficult for people with aphasia and for healthy learners of a second language.

Morphosyntax refers to how word forms change to match other words within a sentence. For example, present tense English verbs typically require an -s if the subject is a third person singular subject (e.g., he often runs). In other languages, such as Spanish, morphosyntactic agreement can involve other features (i.e., number and gender) and affect other word classes (e.g., adjectives and determiners). For example, in the Spanish sentence Los gatos son pequeños, meaning "the cats are small", requires that the adjective pequeños be in the masculine plural form because it must agree with the masculine plural noun gatos. Examining morphosyntax provides us with deep insight into the relationship between abstract grammatical knowledge and successful language use, and conversely, what language issues arise when there are issues with these underlying processes. This is because grammatical morphosyntax requires complex and abstract internal representations of morphological features at the word-level (e.g., number, gender, case) that then must be integrated into larger, sentence-level operations involving multiple words.

My research uses a combination of behavioral and neurolinguistic methodologies, such as electroencephalography (EEG), to investigate whether healthy bilinguals and bilingual individuals with aphasia are using qualitatively similar mechanisms in each language and to what extent second language learners are able to create and use the representations underlying these processes.

Aphasiology

Aphasia is a language disorder that is most often acquired through severe brain injury. Commonly, this language impairment is seen in individuals who have brain damage following a stroke. Nonetheless, the severity of language loss in people with aphasia (PWA) can display a large range. For instance, some may have trouble with recalling the correct vocabulary while others struggle to comprehend or produce even the most basic of sentences. Despite decades of research, PWA often face long periods of intense language rehabilitation with inherently uncertain prognoses. This is especially true for PWA who speak languages other than English. Despite increasing global rates of bilingualism, aphasia research continues to prioritize English, resulting in poorer understanding of aphasic language loss in other languages and thus, poorer outcomes for aphasia rehabilitation in these languages.

My research attempts to expand our understanding of language deficits seen in PWA by looking to non-targetlike morphosyntactic performance in PWA who speak languages other than English. As English is a morphologically impoverished language wherein nouns only inflect for number (e.g. cat-cats), there is often a dearth of information on the morphological characteristics of PWA for features that do not exist in English, such as grammatical gender or case. By looking at multiple features, each with their own set of language-specific and language-general rules, we can begin to identify the sources of morphological variability seen in PWA. For example, is it the case that PWA produce errors with agreement due to deficits at how morphosyntactic features are encoded at the lexical level, or is it the case that these representations are intact yet there is an impairment with syntactic processes themselves?

Second language Acquisition

Second language learning is often an incredibly difficult task for many adult learners. In fact, many of the most advanced second language learners still make frequent grammatical mistakes, especially if the second language differs greatly from the first language. This is often seen with grammatical aspects of the second language, raising the question of why learning the grammar of an additional language is so uniquely challenging? Is it the case that learners are unable to create the necessary representations for novel features of a second language? Or is it that learners are constrained by reduced processing abilities in the second language?

My research addresses these questions by examining how native English speakers fare with agreement in Spanish. This is an interesting language-pairing because English has the feature of number (e.g., this dog vs. these dogs) and Spanish has the feature of number AND gender. That is, every noun in Spanish is assigned either a masculine or feminine gender which dictates the forms of agreeing adjectives and determiners. As such, this provides an exciting test case in which English speakers already have representations for one feature (number) but must acquire a new feature that English does not have (gender).

Neurobiology of multilingualism

The human brain is a finely-tuned and highly structured machine that is capable of incredible feats, typically including the rapid comprehension and production of language. It is well established that the brain's ability to reorganize itself decreases as a person gets older, with the highest levels of neural plasticity seen in the youngest populations. This maturational effect is also seen with language. For example, adult learners of a second language can reasonably be expected to struggle with acquiring a new language and may never master the language, even after years of study. Nonetheless, in instances of brain injury, such as with stroke, the damaged brain is often able to recruit nearby neural structures and repurpose them for a given task. This can be seen in PWA who regain language ability while maintaining areas of lesioned tissue. Nonetheless, PWA who have lesions in similar locations of the brain may have completely different levels of impairment. In fact, in bilingual PWA, it is often the case that each language is affected differently. As such, it is still unclear what the specific relationship between neuroanatomical structures and their linguistic correlates.

My research interests pertain to how the brain stores and processes language, especially for bilinguals who have multiple, distinct grammars simultaneously in one brain. I hope to address questions of whether bilinguals use overlapping neural structures as they store and process each language are stored as separate units within the brain.