Kimberly Crespo’s understanding of the world has always moved seamlessly between English and Spanish. Her Colombian mother and Puerto Rican father spoke mostly Spanish at home, and Crespo and her three siblings felt at ease alternating between languages in their racially and ethnically diverse Elizabeth, N.J., neighborhood.
“Being able to switch between two languages opens up your world,” she says. “The way that meaning and knowledge are encoded differs across languages. For example, in Spanish, you have multiple words that can index different gradients of love. To me, being bilingual provides a linguistic flexibility that’s important.”
Crespo, an assistant professor of speech, language, and hearing sciences, became interested in language development as a teenager, when her youngest brother was diagnosed with a speech delay. While her mother was working, Crespo would bring him to his speech pathology appointments at the local elementary school. “I was fascinated by this idea of him learning language through play,” she recalls.
The first member of her family to attend college, Crespo enrolled at Kean University in Union, N.J. Through a college work-study program, she found a job as an assistant in the speech pathology department and soon connected with a mentor who encouraged her interest in research. Crespo went on to earn her PhD in communication sciences and disorders from the University of Wisconsin–Madison. Since joining Sargent in 2022, Crespo has channeled her passion for dual-language representation into her research.
Language, Cognition, and Bilingualism
As director and principal investigator of the Bilingual Learning Lab (BLL), Crespo explores how the bilingual experience influences language and cognitive development. She wants to understand how bilingual parents speak to and teach their children at home and how dual-language input shapes word-learning and semantic development (how word meanings are represented, organized, and connected). “Most language acquisition studies don’t include bilingual kids or kids with language disorders,” she says, “so we actually don’t know how robust these theories are in other contexts and with other learners.”
It’s a problem compounded by the reality that being bilingual tends to intersect with being lower income. “We know that lower socioeconomic status is tied to poorer language outcomes,” Crespo says. “These studies ultimately inform policy and curriculum. We need to be able to generalize to multiple populations, and that includes kids who are brought up bilingually.”
At the BLL, Crespo says, the goal is to recruit more diverse populations to participate in studies, rather than focusing narrowly on one subgroup or another. “Our approach is to look at the full continuum of language ability, including kids who traditionally fall under a developmental language disorder category,” she says, “That’s just a more equitable—not to mention analytically robust—way of testing how language ability influences children’s learning.”
Last year, Crespo and collaborators at UW–Madison published a study that tested the effect of code-switching, or alternating between two languages, on word-learning in Spanish-English bilingual children. Bilingual parents—especially those who have children with neurodevelopmental disabilities—are routinely advised to speak to their kids in only one language. The assumption is that dual-language input hampers language acquisition.
Crespo’s study found no empirical evidence to support that practice. In fact, her findings suggest that code-switched input does not impede word-learning and that it may enhance vocabulary growth over time. “A crucial practical finding is that children with lower levels of language ability learn just as well from code-switched input as from single-language input,” Crespo says. “This should reassure parents, educators, and clinicians who are concerned that code-switched input may be nonoptimal for children with language difficulties.”
Our approach is to look at the full continuum of language ability, including kids who traditionally fall under a developmental language disorder category. That’s just a more equitable—not to mention analytically robust—way of doing it.
—Kimberly Crespo
Current and Future Research
Crespo’s current research examines how bilingualism influences word-learning in late-talking toddlers. “We know that bilinguals represent meanings of words across two languages,” she says. “A child might know the word ‘ball’ in English but understand the different properties of a ball in Spanish. My question is, how do kids make connections and leverage this information that is encoded in two different languages to learn something new?”
Crespo has a hunch that when bilingual caregivers follow recommendations to limit dual-language exposure to kids with language delays, children may lose the “semantic richness” they would have received from the language they speak at home—to the detriment of their learning outcomes. Preliminary data show that “more bilingual experiences make kids better word learners,” she says. “A longer-term question is, what are the cascading effects of that? Could this help us better understand the variability in language outcomes and language abilities in kids?”
Crespo hopes her lab can lead in advancing research that prioritizes linguistic diversity. “Bilingual families and children bring valuable insights into the adaptability and plasticity of the human brain,” she says. “Embracing the experiences of dual-language learners not only enhances our understanding of language development but also fosters cultural competence and equity in speech-language services. It’s the only way we can create more inclusive and effective therapeutic models for all learners.”
Two PhD candidates in speech, language, and hearing sciences—Erin Carpenter (’20,’25) and Michael Scimeca (’20,’25)—were awarded the prestigious Ruth L. Kirschstein National Research Service Award Individual Predoctoral Fellowship from the National Institutes of Health. The grant provides funding for a dissertation research project as well as a graduate stipend for living expenses. Both Carpenter and Scimeca work with Swathi Kiran, the James and Cecilia Tse Ying Professor in Neurorehabilitation, in BU’s Center for Brain Recovery. The center, which Kiran directs, aims to understand language processing and communication after brain injury.
Using noninvasive neuroimaging techniques, Carpenter will study neural and behavioral differences between monolingual and bilingual individuals in neurotypical and aphasic populations. “There are a lot of theories that bilingualism enhances cognitive function by training other areas of the brain,” Carpenter says. “I hope to be able to show that, in cases of dementia or stroke, bilinguals have more cognitive reserve and resilience to that damage because they rely on different neural regions for certain tasks.”
Scimeca’s research will examine how bilingual individuals with aphasia navigate reading different word or sentence structures after a brain injury. “If we can determine that certain linguistic structures make reading more challenging [for stroke victims], those might be good targets for intervention,” Scimeca says. “If we can train recognition and better comprehension of those structures, it could result in better treatment outcomes and improvement in reading recovery after a stroke.” —Ting Yu