Language development is about far more than learning words \u2013 it is shaped by biological, environmental, and social factors alike. Some children speak in full sentences as early as age 2; others are still naming individual objects at that age. Yet researchers broadly agree on one thing: understanding how children “put together” the words they learn \u2013 the relationship between vocabulary and grammar \u2013 is fundamental to understanding language development as a whole.<\/p>\n\n\n\n
For a long time, the assumption was simple: one area drives the other. Depending on the theory, researchers looked for evidence either that vocabulary shapes grammar, or that grammar shapes vocabulary. One group observed that individual words appear in children\u2019s language before they are combined into simple utterances, concluding that children need to accumulate enough words before they can begin to form sentences. <\/p>\n\n\n\n
Other theories argued that grammar is crucial for vocabulary growth: even very young children rely on grammatical cues to decode the meanings of new words. Many studies also showed that once children begin forming their first sentences, their vocabulary grows rapidly \u2013 they simply need more words to keep building longer utterances. Recent theories, however, propose that the relationship between vocabulary and grammar development is more complex than previously assumed: bidirectional, and likely shifting as the child grows older.<\/p>\n\n\n\n The researchers at the University of Warsaw started from a clear premise: to capture the interplay between vocabulary and grammar development \u2013 and track how children\u2019s linguistic competence shifts over time \u2013 longitudinal studies are essential. These follow the same children over months or even years. In practice, this means asking parents to regularly report on their child\u2019s progress. And that, it turns out, is easier said than done. Such measurements can be genuinely burdensome, demanding significant time and effort from already busy parents.<\/p>\n\n\n\n Adaptive questionnaires may offer a way out. A mobile app developed by Dr. Muszy\u0144ska\u2019s team lets parents report on their child\u2019s language development in a far less time-consuming way. The app uses Computerized Adaptive Testing (CAT) \u2013 a method in which an algorithm continuously tailors questions to the estimated level of the respondent \u2013 making the whole process significantly more efficient.<\/p>\n\n\n\n “In traditional questionnaires, a parent goes through every single test item \u2013 including those that are far too easy or far too difficult for their child. In the adaptive approach, items are selected on the fly: each response helps us estimate the child\u2019s current level and choose the next item accordingly,” says Dr. Karolina Muszy\u0144ska.<\/p>\n\n\n\n In practice, traditional vocabulary checklists asked parents to work through a long list of words and tick those their child already knew. Such lists included words the toddler had mastered months ago along with words they had yet to encounter. Adaptive questionnaires cut through this by building an individualized path through the item bank \u2013 each word the parent is asked about is matched to the child\u2019s current, estimated vocabulary level.<\/p>\n\n\n\n The algorithm, for instance, may skip \u201cmama\u201d or \u201cgrandma\u201d the moment it determines the child already uses more advanced words like “dinosaur” or “bubbles.” Each subsequent question is recalibrated to the child\u2019s level, making the whole process far more manageable \u2013 and allowing parents to track their child\u2019s language regularly, without facing the same exhaustive list every time.<\/p>\n\n\n\n The study, now getting underway, will follow children aged 18 to 36 months \u2013 a crucial window for language development, during which children progress from single words to simple and then increasingly complex sentences. Within just a few months, a toddler\u2019s vocabulary can grow from several dozen to several hundred words, and the first multi-word utterances begin to appear. While observing this process, the team will also analyze the extent to which the child\u2019s environment shapes its dynamics.<\/p>\n\n\n\n “The quantity and quality of the language children hear every day is crucial to their ability to acquire vocabulary and grammatical rules,” emphasizes Dr. Muszy\u0144ska.<\/p>\n\n\n\n To better understand these relationships, the researchers are working with both monolingual children and bilingual children acquiring Polish and Norwegian simultaneously.<\/p>\n\n\n\n Recent research by Dr. Muszy\u0144ska and the MultiLADA team suggests that monolingual and bilingual children do not differ in the rate at which they reach key language development milestones.* Yet bilingual children naturally hear less of each of their languages than monolingual children do. How such differences in language exposure influence the relationship between vocabulary and grammar development remains an open question \u2013 and one with real stakes. Understanding them could be crucial for the accurate assessment of language development and for avoiding misdiagnosis. The \u201cFrom Word to Sentence\u201d project is an important step toward better understanding and supporting bilingual children\u2019s language development.<\/p>\n\n\n\n Results are not expected until 2027. The researchers hope their findings will advance our understanding of how children acquire language \u2013 and how that development can be supported early enough to prevent difficulties from becoming a serious problem once children start school.<\/p>\n\n\n\n The adaptive questionnaire developed by Dr. Muszy\u0144ska\u2019s team is based on the Inwentarz Rozwoju Mowy i Komunikacji<\/em> (IRMiK; Polish adaptation of the MacArthur-Bates Communicative Development Inventory), a tool widely used by clinicians \u2013 and familiar to many parents \u2013 in the early diagnosis of language development. Developing an adaptive version of IRMiK may ultimately allow the lengthy standard questionnaire to be replaced, at least in certain contexts, by a much shorter adaptive version.<\/p>\n\n\n\n The text was originally published in Polish on the Serwis Naukowy UW <\/em>website <\/em><\/a>on May 16, 2025.<\/em><\/p>\n\n\n\n![\"\"](\"https:\/\/serwisnaukowy.uw.edu.pl\/en\/wp-content\/uploads\/2026\/05\/pexels-polesietoys-27661871-kadr-1024x749-1.webp\")
How to study language acquisition?<\/strong><\/h3>\n\n\n\n
“From word to sentence”<\/strong><\/h3>\n\n\n\n