Half the global population communicates in more than one language, yet many individuals struggle to articulate their skills beyond basic descriptors like “bilingual” or “I speak a bit of Spanish.” Researchers at New York University have developed a digital tool that replaces those ambiguous expressions with a specific score, indicating where a person stands on the continuum from monolingual to polyglot.
The instrument requires two simple inputs: the age at which each language was acquired and the level of proficiency in it currently. Using these factors, mathematical equations yield a multilingualism score on a scale from zero to one, in addition to a separate indication of the predominant language. This system accommodates nearly 50 languages, including American Sign Language, and allows users to include any language not already mentioned.
Neuroscientists Esti Blanco-Elorrieta and doctoral candidate Xuanyi Jessica Chen created the calculator to address a practical issue. Studies on bilingualism have traditionally depended on extensive questionnaires or blunt classifications, complicating the comparison of research or accurately reflecting the actual differences among speakers. Physicians treating stroke patients with language impairments encounter similar challenges in determining which language was prioritized by the brain pre-injury.
## Age Holds More Significance Than You Might Think
The formulas used are not random. They are tied to a biological fact: the capacity of the brain to attain native-like proficiency significantly declines after approximately age 10. This threshold becomes a key point in the calculations. For instance, if you began learning Mandarin at age five, the calculator assigns greater significance to that experience than if you started at 25, even if you currently assess your fluency in both languages as equal.
Self-assessments are frequently regarded as unreliable, but the NYU team discovered that they are unexpectedly precise when analyzed across specific skills. The calculator prompts users to evaluate themselves on listening, reading, speaking, and writing separately. This level of detail helps create a clear representation of an individual’s linguistic experience without needing costly lab tests or lengthy interviews.
To corroborate their method, the researchers evaluated the formulas on two groups: healthy young bilingual individuals and older adults with language impairments resulting from strokes or brain injuries. The straightforward calculator generated scores that closely mirrored those from much more complicated statistical approaches. This consistency persisted across both demographics, indicating that the calculations are robust enough to accommodate the diverse range of human experiences.
> “This calculator provides a transparent, quantitative instrument that can be utilized by researchers, clinicians, and educators to better define multilingual populations, ultimately enhancing the quality of research and practical applications from language instruction to clinical evaluation,” Esti Blanco-Elorrieta states.
## From Scientific Inquiry to Clinical Application
The practical ramifications go beyond merely quenching personal curiosity. Physicians could employ the scores to customize aphasia therapy based on the language that a patient’s brain prioritized. Educators might assign students to suitable language classes without depending on standardized assessments that overlook the subtleties of genuine fluency. Cognitive researchers exploring the impact of bilingualism on memory or attention could finally articulate their study groups with accuracy instead of considering “bilingual” as a single category.
For millions who easily switch between languages, the tool provides something more concrete than just a label. It recognizes that language is not merely a binary condition. Rather than posing the question of whether one is bilingual, it shifts to how languages interact and which one takes precedence. Some individuals experimenting with the interface were astonished to find that their second language had subtly become dominant, a transition they sensed but couldn’t express until the figures appeared on the display.
This initiative shifts language science away from rigid classifications and towards a spectrum that accurately portrays how individuals genuinely navigate their linguistic journeys. Every speaker’s path is unique, influenced by their starting age, the amount of practice, and the language their brain defaults to during stress. The calculator does not simplify that complexity; it quantifies it.
[Bilingualism: Language and Cognition: 10.1017/S1366728925100849](https://doi.org/10.1017/S1366728925100849)
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