Putting a figure on a person’s bilingual experience can be daunting.
Esti Blanco-Elorrieta, assistant professor of psychology and neural science at New York University, looks into one way to do so.
Faculty Bio:
I am an Assistant Professor of Psychology and Neural Science at New York University. In my research, I combine insights from monolingual and multilingual individuals, who process language through speech or sign, to inform an inclusive and comprehensive neurobiology of language. My research combines data from neuroimaging, computational and behavioral methods with theoretical insights from linguistics, psychology and neuroscience.
I obtained my PhD from New York University, where I worked at the Neuroscience of Language lab under Liina Pylkkänen’s supervision and completed my post-doctoral training at Harvard University, working in the Cognitive Neuropsychology lab under Alfonso Caramazza’s supervision. In 2019, I was recognized as a Forbes 30 under 30 scientist, and in 2025, I received the Early Career Award from the Society for the Neurobiology of Language.
Transcript:
For decades, bilingualism researchers have faced a deceptively simple question: how do we actually measure how bilingual someone is?
We often collect rich language histories, but when it comes time to analyze the data, there’s no standard way to turn all that information into a single, interpretable number. As a result, different studies define “language dominance” and “degree of bilingualism” in very different ways, making it hard to compare results across labs and populations.
In my research with my collaborator Jessica Chen, we set out to develop a simple, theoretically grounded way to quantify two things: how dominant someone is in one language versus another, and where they fall on the continuum from monolingual to highly multilingual.
We built our approach around two variables that decades of work show are fundamental: self-rated proficiency and age of acquisition. Age of acquisition matters because the brain’s capacity for language learning changes over development, and later exposure typically limits ultimate attainment. Proficiency matters because it reflects how well the language is actually represented and used.
We combined these factors into a formula that produces a continuous dominance score, ranging from perfectly balanced bilinguals to strongly dominant speakers of one language. We also introduced a multilingualism score that places individuals on a spectrum from monolingual to polyglot, while giving diminishing weight to each additional language, reflecting the fact that the jump from one to two languages is larger than from four to five.
We validated these measures in large datasets, including both healthy adults and bilingual individuals with aphasia, and showed that our simple formulas closely match much more complex statistical methods.
Our goal is to offer the field a transparent, biologically informed, and easily reproducible way to characterize language experience—so that when we talk about bilingualism, we’re finally speaking the same quantitative language.
Read More:
[NYU] - Neuroscientists Devise Formulas to Measure Multilingualism
